Ch.16 - Aqueous Equilibrium WorksheetSee all chapters
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Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
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Ch.23 - Transition Metals and Coordination Compounds
Identifying a Buffer

A buffer is a solution composed of a weak acid with its conjugate base. 

Concept #1: Understanding a Buffer.

Buffers resist drastic changes to the pH if a strong acid or strong base is added. 

If a strong base is added then the buffer resists a pH change by having the weak acid neutralize it. 

If a strong acid is added then the buffer resists a pH change by having the conjugate base neutralize it. 

Practice: Which one of the following combinations does not create a buffer?

Practice: Which of the following combinations can result in the formation of a buffer?

Buffer Creation

As we stated earlier a buffer is composed of a weak acid and its conjugate base, but there are actually three ways to create a buffer.

Concept #2: Method 1 for  Creating a Buffer. 

The first and most obvious way to create a buffer is to simply combine a weak acid and its conjugate base. In this case, a buffer is most ideal when both components are highly concentrated and equal to one another. 

The weak acid and conjugate base can be different from one another by up to a magnitude of 10. This is called the buffer range. If they are different by more than 10 then this is considered a bad buffer.

Concept #3: Method 2 for Creating a Buffer. 

The second method in creating a buffer is mixing a strong acid with a weak base. In this case since we have a strong species mixing with a weak species then we must make sure the weak species is higher in amount. 

Concept #4: Method 3 for  Creating a Buffer.

The third method in creating a buffer is mixing a strong base with a weak acid. In this case since we have a strong species mixing with a weak species then we must make sure the weak species is higher in amount. 

Example #1: Which of the following combinations can result in the formation of a buffer?

a)     0.01 moles HClO (hypochlorous acid) and 0.05 moles of NaOH.

b)     0.01 moles HClO (hypochlorous acid) and 0.05 moles of HCl.

c)     0.01 moles HClO (hypochlorous acid) and 0.05 moles of NH3.

d)     0.01 moles HClO (hypochlorous acid) and 0.001 moles of NaOH

Practice:  Which of the following combinations can result in the formation of a buffer?

Practice: A buffer solution is comprised of 50.0 mL of a 0.100 M HC2H3O2 and 60.0 mL of a 0.100 M NaC2H3O2. Which of the following actions would completely destroy the buffer?

Henderson – Hasselbalch Equation

Concept #5: The Henderson – Hasselbalch Equation.

Whenever we have a buffer we can skip the ICE Chart and use the Henderson Hasselbalch. 

Example #2: What is the pH of a solution consisting of 2.75 M sodium phenolate (C6H5ONa) and 3.0 M phenol (C6H5OH). The Ka of phenol is 1.0 x 10-10

Practice: Calculate the pH of a solution formed by mixing 200 mL of a 0.400 M C2H5NH2 solution with 350 mL of a 0.450 M C2H5NH3solution. (Kb of C2H5NHis 5.6 x 10 -4).

Example #3: What is the buffer component concentration ratio, [Pr ] / [HPr] , of a buffer that has a pH of 5.11. (The Ka of HPr is 1.30 x 10-5). 

Example #4: Over what pH range will an oxalic acid (H2C2O4) / sodium oxalate (NaHC2O4) solution work most effectively? The acid dissociation constant of oxalic acid is 6.0 x 10-2.

a) 0.22 – 2.22        b) 1.00 – 3.00        c) 0.22 – 1.22        d) 2.0 – 4.0

Practice: Determine how many grams of sodium acetate, NaCH3CO2 (MW: 82.05 g/mol), you would mix into enough 0.065 M acetic acid CH3CO2H (MW: 60.05 g/mol) to prepare 3.2 L of a buffer with a pH of 4.58. The Ka is 1.8 x 10-5.

Example #5: Which weak acid-conjugate base combination would be ideal to form a buffer with a pH of 4.74.

a)     Cyanic acid and Potassium cynate           (Ka = 4.9 x 10-10)

b)     Benzoic acid and Lithium benzoate         (Ka = 6.3 x 10-5)

c)     Acetic acid and Sodium acetate                   (Ka = 1.7 x 10-5)

d)     Ammonium chloride and Ammonia         (Ka = 5.56 x 10-10)

e)     Formic acid and Cesium formate                (Ka = 1.7 x 10-4)

Practice: A buffer solution is made by combining a weak acid with its conjugate salt. What will happen to the pH if the solution is diluted to one-fourth of its original concentration?

Additional Problems
What is the pH of a buffer solution that contains 0.55 M methylamine, CH 3NH2, and 0.29 M of methylammonium chloride, CH3NH3Cl? A. 3.63 B. 10.32 C. 10.92 D. 10.37 E. 3.08
Which pair of substance can be dissolved together (in the right ratio) to prepare a buffer solution? i, C2H3O2H ii. NaC2H3O2 iii. NaOH iv. HCl v. NaCl A. i and ii B. i and iii C. ii and iii D. i and ii, ii and iv, i and iii E. iv and v; i and iii
Calculate the pH of a solution made by mixing 8.627 g of sodium butanoate in enough 0.452 M butanoic acid, HC4H7O2 , to make 250.0 mL of solution. A. 4.75 B. 4.82 C. 5.00 D. 2.58 E. 4.65
Which of the following solutions is a good buffer system? A) A solution that is 0.10 M HC2H3O2 and 0.10 M LiC2H3O2 B) A solution that is 0.10 M HBr and 0.10 M KC 2H3O2 C) A solution that is 0.10 M HI and 0.10 M NH 4+ D) A solution that is 0.10 M NaOH and 0.10 M KOH E) None of the above are buffer systems.
If a biochemist wishes to prepare a buffer that will be effective at a pH of 3.0 (at 25°C) for studying peptide degradation, what will be the best choice for the acid component? (a) Oxalic acid (H2C2O4), Ka = 5.9 x 10 -2 (b) Hydrofluoric acid (HF), Ka = 6.6 x 10 -4 (c) Pyridinium ion (HC5H5N+ ), Ka = 5.6 x 10 -6 (d) Hypochlorous acid (HClO), Ka = 3.0 x 10 -8 (e) Hydrocyanic acid (HCN), Ka = 6.17 x 10 -10 
How much sodium lactate NaC3H3O3, should be added to 583.58 mL of a 0.473 M lactic acid, HC3H3O3, solution to make a buffer of pH 4.08? (assume any change in volume is insignificant and that  the pKa is rounded to two significant figures) a. 6.986 grams b. 1.157 grams c. 127.4 grams d. 17.89 grams e. 51.59 grams
Which one of the following pairs of substances cannot be mixed together (in any quantities) to form a buffer solution? (a) H3PO4, KH2PO4 (b) NH3, NH4Cl (c) HNO2, NaNO2 (d) CH3COONa, CH3COOHa (e) HNO3, KOH  
The Henderson–Hasselbalch (H-H) equation is a clever rearrangement of the  Ka equilibrium expression that comes in very handy for certain pH calculations. The H-H equation can be used to calculate the buffer ratio ([base]/[acid]) required to prepare a buffer at a specific pH. It is possible that the buffer ratio required to prepare a pH 6.85 buffer could be used to study novel chemotherapy agents; however, the noble H-H equation can be used for more nefarious purposes.
Which of the following weak acids would be BEST to use to make a buffer of pH = 2.90 a. lactic b. butanoic c. chloroacetic d. benzoic e. hypochlorous
Which of the following weak acids would be BEST to use to make a buffer of pH = 3.52? a. nitrous acid b. hydrofluoric acid c. chloroacetic acid d. lactic acid e. benzoic acid
The pH of a sodium acetate-acetic acid buffer is 4.50. Calculate the ratio of [CH3COO- ]/[CH3COOH].
A solution contains 1.00 mole of acetic acid and has pH = 2.50. How many grams of NaCH3COO·3H2O (of MW 136) should be dissolved in the solution to raise the pH to 4.00? 1. 10 g 2. 35 g 3. 20 g 4. 15 g 5. 24 g
Which one of the following combinations CANNOT function as a buffer solution? A)        H2C2O4 and CsHC2O4             D)       HF and LiF B)        NH3 and (NH4)2SO4                 E)        HCl and NaCl C)        K2HPO4 and KH2PO4             
Calculate the pH of a buffer solution that contains 0.25 M chloroacetic acid (ClCH2CO2H) and 0.15 M sodium chloroacetate (ClCH2CO2Na).  [Ka = 1.4 × 10–3  for chloroacetic acid] A)  3.07    B)  2.85    C)  4.19    D)  2.63    E)  4.41
You are asked to go into the lab and prepare a buffer solution with a pH of 6.40 ± 0.2.  Which weak acid would be the best choice?             A)  carbonic acid                                Ka = 4.2 x 10-7                B)  phenol                                           Ka = 1.3 x 10-10                C)  ascorbic acid                                 Ka = 8.0 x 10-5                D)  hydrosulfuric acid                          Ka = 9.5 x 10-8                E)  potassium hydrogen phthalate      Ka = 3.1 x 10-6    
Explain why the salt of a weak acid, as well as the acid itself, must be present to form a buffer solution. 1. The anion from the salt is needed to partially neutralize added base. 2. The anion from the salt is needed to partially neutralize added acid. 3. The cation from the salt is needed to partially neutralize added acid. 4. The cation from the salt is needed to partially neutralize added base. 5. Actually, a weak acid by itself is a buffer; no salt is needed. 
Identify a good buffer. A) small amounts of both a weak acid and its conjugate base B) significant amounts of both a strong acid and a strong base C) small amounts of both a strong acid and a strong base D) significant amount of both a weak acid and a strong acid E) significant amounts of both a weak acid and its conjugate base
A student is asked to prepare a buffer solution at pH = 8.60 using one of the following weak acids: HA (Ka = 2.7 x 10-3), HB(Ka= 4.4x10-6), HC (Ka = 2.6 x 10-9), Which acid should she choose?
You wish to prepare an HC 2H3O2 buffer with a pH of 4.24. If the pK a of is 4.74, what ratio of C2H3O2- / HC2H3O2 must you use? A) 0.10 B) 0.50 C) 0.32 D) 2.0 E) 2.8
Blood contains a buffer of carbonic acid (H2CO3) and hydrogen carbonate ion (HCO3-) that keeps the pH at a relatively stable 7.40. What is the ratio of [HCO3-] / [H2CO3] in blood? Ka1 = 4.30x10-7 for H2CO3.  0.0926 10.8 3.98 x 10-8 1.71 x 10-14
One liter of a buffer from the blood is found to have 0.4 moles of acid (pK a = 4.76) and 0.1 moles of conjugate base. a. Is this pH of buffer greater than, equal to, or less than 4.76? Show your reasoning mathematically?   b. You want to get the buffer to maximum buffering capacity. You have HCl and NaOH available. Which would you add and how much in terms of moles? c. Is the pH of the buffer after step b greater than, equal to, or less than to 4.76?    
What is the effective pH range of the pyridine/pyridinium chloride buffer? For pyridine, the value of Kb is 1.8 x 10-9. (a) 9.1-11.1 (b) 1.4-3.4 (c) 10.3-12.3 (d) 7.7-9.7 (e) 4.3-6.3  
A solution was made by dissolving 0.1219 moles of sodium acetate in 200.0 mL of  1.00 M acetic acid.  Assuming the change in volume when the sodium acetate is not significant, estimate the pH of the solution. The Ka for acetic acid is 1.7 x 10-5.    A.  5.42   B.  7.31   C.  9.42   D.  4.56   E.  2.89
Which of the following procedures will result in the largest change in pH? Adding NaNO2 to a solution of HNO2 in water or  Adding NaNO3 to a solution of HNO3 in water  
The addition of hydrochloric acid and __________ to water produces a buffer solution. a. HC6H5O   b. NaOH c. NH3 d. HNO3 e. NaNO3
Which one of the following pairs, when mixed, do not form a buffered solution? a) 1.0 M CH3CH2NH2/1.0 M CH3CH2NH3Cl b) 1.0 M CH3CH2COOH/1.0 M CH3CH2COONa c) 1.0 M KOH/1.0 M HI d) 1.0 M NH3/1.0 M NH4Cl e) 1.0 M H3PO4/1.0 M KH2PO4
A buffer solution is made by combining a weak acid with its conjugate salt. What will happen to the pH if the solution is diluted to one-half of its original concentration? a) The pH will increase. b) The pH will decrease. c) The pH will remain constant. d) The solution will become more neutral. 
Which weak acid-conjugate base combination would be the best to create a solution with a pH of 4.193?      a)  Butanoic acid and Potassium butanoate (Ka = 1.5 x 10-5)      b)  Benzoic acid and Sodium benzoate (Ka = 6.3 x 10-5)      c)  Acetic acid and Lithium acetate (Ka = 1.8 x 10-5)      d)  Ammonium chloride and Ammonia (Kb = 1.8 x 10-5)      e)  Hypochlorous acid and sodium hypochlorite (Ka = 2.9 x 10-8)
Over what pH range will an oxalic acid (H 2C2O4) / sodium oxalate (NaHC2O4) solution work most effectively? The acid dissociation constant of oxalic acid is 6.0 x 10-2. a) 0.22 – 2.22                 b) 1.00 – 3.00                  c) 0.22 – 1.22                   d) 2.0 – 4.0
What is the pH of a solution which is 0.400 M in dimethylamine (CH 3)2NH) and 0.600 M in dimethylamine hydrochloride (CH3)2NH2+Cl−)? Kb for dimethylamine = 0.00074. 1. 10.78 2. 2.95 3. 10.87 4. 3.31 5. 10.69  6. 11.05 7. 11.21
Find the pH of a buffer solution made by mixing 100 mL of 0.20 M methylamine, CH3NH2, with 250.0 mL of a 0.50 M CH  3NH3Cl. Kb of methylamine is 4.4 x 10-4.   
How many moles of solid NaF would have to be added to 1.0 L of 1.90   M HF solution to achieve a pH of 3.35? Assume there is no volume change. (Ka for HF = 7.2 x 10 -4)       
Which of the following buffer systems would you use to create a buffer with a pH of 4.0? The Ka of nitrous acid, HNO2 is 4.5 x 10-4. a) 0.30 M HNO2 / 0.22 M NaNO2 b) 0.22 M HNO2 / 0.30 M NaNO2 c) 0.11 M HNO2 / 0.50 M NaNO2 d) 0.50 M HNO2 / 0.11 M NaNO2 e) 0.30 M HNO2 / 0.30 M NaNO2
To create a buffer that maintains a pH around 7.54, which solution would you choose? A. CH3COOH and NaCH3COO B. HClO and KClO C. NaOH and HCN D. HNO3 and KNO3
Calculate the pH of a buffer that is 0.225 M HC 2H3O2 and 0.162 M KC2H3O2. The Ka for HC2H3O2 is 1.8 × 10-5.  A) 4.89 B) 9.11 C) 4.74 D) 9.26 E) 4.60
Which of the following is TRUE? A) An effective buffer has a [base]/[acid] ratio in the range of 10 - 100. B) A buffer is most resistant to pH change when [acid] = [conjugate base] C) An effective buffer has very small absolute concentrations of acid and conjugate base. D) A buffer can not be destroyed by adding too much strong base. It can only be  destroyed by adding too much strong acid. E) None of the above are true.  
Which of the following solutions is a good buffer system? A) A solution that is 0.10 M NaCl and 0.10 M HCl B) A solution that is 0.10 M HCN and 0.10 M LiCN C) A solution that is 0.10 M NaOH and 0.10 M HNO 3 D) A solution that is 0.10 M HNO3 and 0.10 M NaNO 3 E) A solution that is 0.10 M HCN and 0.10 M KI
Which of the following acids and their conjugate base would form a buffer with a pH of 8.10?   A. HClO3 pKa= 7.54 B. H2SO3 pKa= 1.77 C. HC2H3O2 pKa= 4.74 D. HNO2 pKa= 3.34 E. HIO pKa= 10.64
Which of the following acids and their conjugate base would form a buffer with pH of 3.34? HClO Ka = 2.9 x 10 –8 C6H5CO2H Ka = 6.5 x 10 –5 HF Ka = 3.5 x 10 –4 HIO3 Ka = 1.7 x 10 –1 HClO2 Ka = 1.1 x 10 –2
A buffer is prepared using 0.085M formic acid and 0.085M sodium formate. Which of the following statements is false?  
An aqueous solution contains 0.26M hydrocyanic acid, HCN. One liter of this solution could be converted to a buffer by the addition of:    
What is the pH of a solution of 0.46 M acid and 0.36 M of its conjugate base if the pKa is 5.51? a) 4.70 b) 4.90 c) 5.20 d) 5.40 e) 5.62
Determine how many grams of potassium hypochlorite, KClO (MW: 90.55 ), you would mix into enough 0.055 M hypochlorous acid, HClO (MW: 52.46 ) to prepare 5.0 L of a buffer with a pH = 6.77. Ka of HClO is 2.9 x 10-8.
A buffer: a. can be made by a combination of a strong acid and strong base. b. can be a combination of a weak acid and its conjugate base. c. resists changes in pH. d. both A and C e. both B and C
A buffer solution is comprised of 50.0 mL of a 0.100 M HC 2H3O2 and 60.0 mL of a 0.100 M NaC2H3O2. Which of the following actions would completely destroy the buffer? a) Adding 0.003 mol HC2H3O2 b) Adding 0.007 mol Ca(C2H3O2)2 c) Adding 0.005 mol NaH d) Adding 0.004 mol HNO3
Which weak acid-conjugate base combination would be the best to create a solution with a pH of 7.538? a) Butanoic acid and Potassium butanoate (Ka = 1.5 x 10 -5) b) Benzoic acid and Sodium benzoate (Ka = 6.3 x 10 -5) c) Acetic acid and Lithium acetate (Ka = 1.8 x 10 -5) d) Ammonium chloride and Ammonia (Kb = 1.8 x 10 -5) e) Hypochlorous acid and sodium hypochlorite (Ka = 2.9 x 10 -8)
Which of the following is TRUE? a) An effective buffer has a [base]/[acid] ratio in the range of 10 - 100. b) A buffer is most resistant to pH change when [weak acid] = [conjugate base] c) An effective buffer has very small absolute concentrations of weak acid and conjugate base. d) A buffer cannot be destroyed by adding too much strong base, it can only be destroyed by adding too much strong acid.  e) None of the above are true.
Which of the following combinations can result in the formation of a buffer? a) HBr and NH4Cl b) LiOH and HNO3 c) H3PO4 and LiH2PO4 e) None of these combinations result in a buffer.
To create a buffer that maintains a pH around 7.54, which solution would you choose? A. CH3COOH and NaCH3COO B. HClO and KClO C. NaOH and HCN D. HNO3 and KNO3
Which of the following combinations can result in the formation of a buffer? a) 90 mL of 0.10 M HCN with 70 mL of 0.10 M NH  3. b) 70 mL of 0.10 M HC 2H3O2 with 30.0 mL of 0.15 M Ba(OH) 2. c) 50 mL of 0.10 M HNO3 with 50 mL of 0.10 M NaOH. d) 70 mL of 0.10 M HNO2 with 25 mL of 0.10 M LiH. e) 70 mL of 0.10 M HClO with 70 mL of 0.10 M LiOH. 
What is the pH of a solution that is 0.2 M in acetic acid (Ka= 1.8 x 10  -5) and 0.2 M in sodium acetate? A. 4.7 B. 9.3 C. 7.0 D. 5.4 E. 8.6
Which of the following pairs of solution does not produce a buffer? A. 0.3 M HClO3 & 0.2 M KOH B. 0.2 M NH3 & 0.1 M HClO4 C. 1.5 M HF & 1 M LiOH D. 0.1 M KCOOH & 0.1 M NaCOOH
Consider a solution consisting of the following two buffer systems: H2CO3    ⇌ HCO3 - + H +          pKa = 6.4 H2PO4 -   ⇌ HPO4-2 + H +         pKa = 7.2 At pH 6.4, which one of the following is TRUE of the relative amounts of acid and conjugate base present? A) [H2CO3] = [HCO3 - ] and [H2PO4 - ] > [HPO4 -2 ] B) [H2CO3] > [HCO3 - ] and [H2PO4 - ] > [HPO4 -2 ] C) [H2CO3] = [HCO3 - ] and [HPO4 -2 ] > [H2PO4 - ] D) [HCO3 - ] > [H2CO3] and [HPO4 -2 ] > [H2PO4 - ]  E) [H2CO3] > [HCO3 - ] and [HPO4 -2] > [H2PO4 -]
How many moles of solid NaF would have to be added to 1.0 L of 1.90 M HF solution to achieve a buffer of pH 3.35? Assume there is no volume change. (Ka for HF = 7.2 x 10 -4) A. 3.1 B. 2.3 C. 1.6 D. 1.0 E. 4.9 
Calculate the pH of a buffer that is 0.145M in acetic acid and 0.202M in sodium acetate. The acid dissociation constant for acetic acid 1.75x10 –5. 4.60 4.89 5.05 4.74 9.01
Calculate the pH of a solution that is 0.210M in nitrous acid and 0.290M in potassium nitrite. The acid dissociation constant of nitrous acid is 4.50x10 –4. 3.21 3.49 13.86 10.51 4.56
Which of the following acids and their conjugate base would form a buffer with a pH of 8.10? HClO3 pKa = 7.54 H2SO3 pKa = 1.77 HC2H3O2 pKa = 4.74 HNO2 pKa = 3.34 HIO pKa = 10.64
Two compounds, HA & HB have the same K a value. If a solution is prepared containing 0.5  mole of HA and 0.5 of NaB which of the following is True? A) The solution pH = pKa but it has no Buffer Capacity B) The solution is not a Buffer because there is no conjugate base of A or conjugate acid of B-. C) This solution is a good Buffer because the [weak base] = [weak acid] D) The pH = pKb for the B- E)  It is not possible to determine if this is a good buffer or not.
The following boxesrepresent aqueous solutions containing a weak acid, HX, and its conjugate base, X- . Water molecules and cations are not shown.Which solution has the highest pH?
Suppose that a buffer contains equal amounts of a weak acid and its conjugate base. What happens to the relative amounts of the weak acid and conjugate base when a small amount of strong acid is added to the buffer? What happens when a small amount of strong base is added?
What factors influence the effectiveness of a buffer? What are the characteristics of an effective buffer?
What is the effective pH range of a buffer (relative to the pKa of the weak acid component)?
You are asked to prepare a pH = 3.00 buffer solution starting from 1.25 L of a 1.00 M solution of hydrofluoric acid (HF) and an excess of sodium fluoride (NaF).What is the pH of the hydrofluoric acid solution prior to adding sodium fluoride?
What reaction that occurs when HCl is added to a buffer solution composed of HC2H3O2 and NaC2H3O2.
How does the buffer keeps the pH approximately the same even though a strong acid is added.
Calculate the pH of a buffer that is 0.13 M in lactic acid and 0.11 M in sodium lactate.
Calculate the pH of a buffer formed by mixing 85 mL of 0.13 M lactic acid with 95 mL of 0.16 M sodium lactate.
What is the ratio of HCO3- to H2CO3 in blood of pH 7.4?
What is the ratio of HCO3- to H2 CO3 in an exhausted marathon runner whose blood pH is 7.2?
Find the mass of sodium formate that must be dissolved in 310.0 cm3 of a 1.3 M solution of formic acid to prepare a buffer solution with pH = 3.40.
A buffer contains the weak acid HA and its conjugate base A-. The weak acid has a pKa of 4.82 and the buffer has a pH of 4.25.Which buffer component would you add to change the pH of the buffer to 4.72?
What should the molar concentrations of benzoic acid and sodium benzoate be in a solution that is buffered at a pH of 4.63 and has a freezing point of -2.0 oC? (Assume complete dissociation of sodium benzoate and a density of 1.01 g/mL for the solution.)
Derive an equation similar to the Henderson–Hasselbalch equation for a buffer composed of a weak base and its conjugate acid. Instead of relating pH to pKa and the relative concentrations of an acid and its conjugate base (as the Henderson–Hasselbalch equation does), the equation should relate pOH to pKb and the relative concentrations of a base and its conjugate acid.
You have to prepare a pH 3.60 buffer, and you have the following 0.10 M solutions available: HCOOH, CH3COOH, H3PO4, HCOONa, CH3COONa, and NaH2PO4.How many milliliters of HCOOH and HCOONa would you use to make approximately a liter of the buffer?
A buffer is prepared by adding 21.0 g of sodium acetate (CH3 COONa) to 510 mL of a 0.155 M acetic acid (CH3 COOH) solution.Determine the pH of the buffer.
What is the Henderson-Hasselbalch equation?
A mixture of Na2CO3 and NaHCO3 has a mass of 82.1 g . It is dissolved in 1.00 L of water and the pH is found to be 9.92.Find the mass of NaHCO3 in the mixture.
What is the pH of a buffer solution when the concentrations of both buffer components (the weak acid and its conjugate base) are equal? What happens to the pH when the buffer contains more of the weak acid than the conjugate base? More of the conjugate base than the weak acid?
How do you use the Henderson-Hasselbalch equation to calculate the pH of a buffer containing a base and its conjugate acid? Specifically, how do you determine the correct value for pKa?
You have to prepare a pH 5.05 buffer, and you have the following 0.10M solutions available: HCOOH, HCOONa, CH3COOH, CH3COONa, HCN, and NaCN.How many milliliters of each solution would you use to make approximately a liter of the buffer?
Solve an equilibrium problem (using an ICE table) to calculate the pH of of each solution:a solution that is 0.18 M in HCHO2 and 0.13 M in NaCHO2
Solve an equilibrium problem (using an ICE table) to calculate the pH of of each solution:a solution that is 0.14 M in NH3 and 0.19 M in NH4 Cl
Use the Henderson-Hasselbalch equation to calculate the pH of each solution:a solution that is 0.18 M in HCHO2 and 0.13 M in NaCHO2
Use the Henderson-Hasselbalch equation to calculate the pH of each solution:a solution that is 0.14 M in NH3 and 0.20 M in NH4Cl
Use the Henderson–Hasselbalch equation to calculate the pH of each solution:a solution that is 0.125 M in HClO and 0.175 M in KClO
Use the Henderson–Hasselbalch equation to calculate the pH of each solution:a solution that is 0.160 M in propanoic acid and 0.120 M in potassium propanoate
Derive an equation similar to the Henderson-Hasselbalch equation relating the pOH of a buffer to the pKb of its base component.
Use the Henderson–Hasselbalch equation to calculate the pH of each solution:a solution that is 14.5 g of HF and 25.0 g of NaF in 125 mL of solution
Calculate the pH of the solution that results from each of the following mixtures.55.0 mL of 0.17 M HCHO2 with 80.0 mL of 0.13 M NaCHO2
What mass of sodium benzoate should be added to 160.0 mL of a 0.16 M benzoic acid solution in order to obtain a buffer with a pH of 4.30?
A biochemist needs 750 mL of an acetic acid-sodium acetate buffer with exttip{pH}{pH} = 4.55. Solid sodium acetate (CH3 COONa) and glacial acetic acid (CH3 COOH) are available. Glacial acetic acid is 99% CH3 COOH by mass and has a density of 1.05 g/mL. If the buffer is to be 0.25 M in CH3 COOH, how many grams of CH3 COONa must be used?
A biochemist needs 750 mL of an acetic acid-sodium acetate buffer with exttip{pH}{pH} = 4.55. Solid sodium acetate (CH3 COONa) and glacial acetic acid (CH3 COOH) are available. Glacial acetic acid is 99% CH3 COOH by mass and has a density of 1.05 g/mL.How many milliliters of glacial acetic acid must be used?
Derive the Henderson–Hasselbalch equation.
What pH buffer solution is needed to give a Mg2+ concentration of 3.0×10−2 M in equilibrium with solid magnesium oxalate?
If solutions of NH4Cl(aq) and NH3(aq) are mixed, which ions in the resulting solution are spectator ions in any acid-base chemistry occurring in the solution?
The drawing represents a buffer composed of equal concentrations of a weak acid, HX, and its conjugate base, X-. The heights of the columns are proportional to the concentrations of the components of the buffer.Which of the three drawings (1), (2), (3) represents the buffer after the addition of a strong acid?
The drawing represents a buffer composed of equal concentrations of a weak acid, HX, and its conjugate base, X-. The heights of the columns are proportional to the concentrations of the components of the buffer.Which of the three represents the buffer after the addition of a strong base?
The drawing represents a buffer composed of equal concentrations of a weak acid, HX, and its conjugate base, X-. The heights of the columns are proportional to the concentrations of the components of the buffer.Which of the three represents a situation that cannot arise from the addition of either an acid or a base?
You have to prepare a pH 3.60 buffer, and you have the following 0.10 M solutions available: HCOOH, CH3COOH, H3PO4, HCOONa, CH3COONa, and NaH2PO4.Which solutions would you use?
What is a buffer? How does a buffer work? How does it neutralize added acid? Added base?
You have to prepare a pH 5.05 buffer, and you have the following 0.10M solutions available: HCOOH, HCOONa, CH3COOH, CH3COONa, HCN, and NaCN.Which solutions would you use?
You are asked to prepare a pH = 3.00 buffer solution starting from 1.25 L of a 1.00 M solution of hydrofluoric acid (HF) and an excess of sodium fluoride (NaF).How many grams of sodium fluoride should be added to prepare the buffer solution? Neglect the small volume change that occurs when the sodium fluoride is added.
A buffer contains significant amounts of acetic acid and sodium acetate.Write an equation showing how this buffer neutralizes added acid (HCl).
A buffer contains significant amounts of acetic acid and sodium acetate.Write an equation showing how this buffer neutralizes added base (NaOH).
A buffer contains significant amounts of ammonia and ammonium chloride.Write an equation showing how this buffer neutralizes added acid (HCl).
A buffer contains significant amounts of ammonia and ammonium chloride.Write an equation showing how this buffer neutralizes added base (NaOH).
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.100.0 mL of 0.10 M NH3; 100.0 mL of 0.15 M NH4Cl;
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.50.0 mL of 0.10 M ; 35.0 mL of 0.150 M NaOH
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.50.0 mL of 0.15 M HF; 20.0 mL of 0.15 M NaOH
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.175.0 mL of 0.10 M NH3; 150.0 mL of 0.12 M NaOH
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.125.0 mL of 0.15 M NH3; 150.0 mL of 0.20 M
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.75.0 mL of 0.10 M HF; 55.0 mL of 0.15 M NaF
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.150.0 mL of 0.10 M HF; 135.0 mL of 0.175 M HCl
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.165.0 mL of 0.10 M HF; 135.0 mL of 0.050 M KOH
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.125.0 mL of 0.15 M CH3 NH2; 120.0 mL of 0.25 M CH3 NH3Cl
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.105.0 mL of 0.15 M CH3 NH2; 95.0 mL of 0.10 M HCl
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer:75.0 mL of 0.10M HF  55.0 mL of 0.15 M NaF
Find the ratio of the volumes of NaC 3H5O3 soloution to HC3H5O3 (lactic acid) required to prepare a buffer with a pH of 3.90. The solutions are equal in molarity. Ka = 1.4x10-4 for HC3H5O3.
Calculate the pH of a buffer that is 0.225 M HC 2H3O2 and 0.162 M KC2H3O2. The Ka for HC2H3O2 is 1.8 × 10-5.
75.0 mL of 0.10 M HF; 55.0 mL of 0.15 M NaFa. this will be a bufferb. this will not be a buffer 
150.0 mL of 0.10 M HF; 135.0 mL of 0.175 M HCla. this will be a bufferb. this will not be a buffer
165.0 mL of 0.10 M HF; 135.0 mL of 0.050 M KOHa. this will be a bufferb. this will not be a buffer 
125.0 mL of 0.15 M CH3NH2; 120.0 mL of 0.25 M CH3NH3Cl a. this will be a bufferb. this will not be a buffer 
105.0 mL of 0.15 M CH3NH2; 95.0 mL of 0.10 M HCla. this will be a bufferb. this will not be a buffer 
Which pair of compounds will form a buffer in aqueous solution? A. HCl and NaOH B. NaCN and KCN C. HCN and HCl D. HCN and NaCN E. NaCN and NaOH F. HCl and NaCl
CN- is the conjugate base to the weak acid HCN, with K a = 6.0 x 10 -10, pKa = 9.22.Given a 50mL of a 0.1 M of NaCN (which dissociates completely), how many mL of 1.0 M HCl should be added to the solution in order to to bring the pH to 9.22?
Calculate the pH of a solution created by mixing 168.9 mL of 0.395 M Butanoic acid, HC4H7O2, with 293.8 mL of 0.189 M Potassium hydroxide, KOH. The K  a of butanoic acid is 1.5 x 10-5. a. 5.52b. 5.14c. 4.90d. 4.74e. 4.50
Complete this table of initial and final concentrations.              HF(aq) + KOH(aq) → KF(aq) + H  2O(l)Initial:    2.0 M      1.0M            0MFinal:Which of the following best describes the final solution?a. a neutral salt solutionb. a bufferc. none of the above
What mass of solid NaCH3CO2 (molar mass=82.0 g/mol) should be added to 1.0 L of 0.50 M CH3CO2H to make a buffer with a pH of 7.21? (pKa of CH 3CO2​H = 7.21)  
Which of the following solutions is a good buffer system?a. A solution that is 0.10 M HC2H3O2 and 0.10 M LiC2H3O2b. A solution that is 0.10 M HF and 0.10 M NaC 2H3O2c. A solution that is 0.10 M NaOH and 0.10 M KOHd. A solution that is 0.10 M HCl and 0.10 M NH 4+e. None of the above are buffer systems
Which one of the following pairs cannot be mixed together to form a buffer solution? Why?a. NH3, NH4Clb. NaC2H3O2, HCl (C2H3O2- = acetate)c. RbOH, HBrd. KOH, HFe. H3PO4, KH2PO4
The addition of hydrofluoric acid and __________ to water produces a buffer solution. Why / how?a. HClb. NaNO3c. NaFd. NaCle. NaBr
Which of the following solutions could be classified as a buffer?a. 0.100 M HCl and 0.100 M NH4Clb. 0.100 M HBr and 0.100 M KBrc. 0.100 M HNO2 and 0.100 M NaNO2d. 0.100 M HCl and 0.100 M NaOH 
Which of the following buffer systems would be the best choice to create a buffer with pH = 9.05? a. HF / KFb. HNO2 / KNO2c. NH3 / NH4Cld. HClO / KClO
What mass of ammonium chloride, NH 4Cl, (Ka = 5.6 x 10 -10) must be added to exactly 500mL of 0.10M NH3 solution to give a solution with a pH of 9.00?
What is the pH of a solution prepared by mixing 0.250 mol of benzoic acid (C6H5COOH, Ka=6.50 x 10 –5) and 0.150 mol of sodium benzoate (C6H5COONa) in sufficient water to yield a 1.00 L solution? a) 3.965 b) 4.190 c) 4.411 d) 7.321 e) 10.084
At a pH of 7.40, what is the ratio of the molar concentrations of PO 43− to HPO42−?Express your answer using two significant figures.
Which of the following solutions is a buffer? Check all that apply.a. A solution made by mixing 100 mL of 0.100 M HCOOH and 500 mL of 0.100 M NaOH.b. A solution made by mixing 100 mL of 0.100 M HCOOH and 50 mL of 0.100 M NaOH.c. A solution made by mixing 100 mL of 0.100 M HCOOK and 50 mL of 0.100 M KCl.d. A solution made by mixing 100 mL of 0.100 M HCOOH and 50 mL of 0.100 M HCl.
At a pH of 7.40, what is the ratio of the molar concentrations of H 2PO4− to H3PO4?Express your answer using two significant figures.
Which pair of compounds will form a buffer in aqueous solution? a. HCN and NaCN b. HCl and NaOH c. NaCN and NaOH d. HCN and HCl e. HCl and NaCl f. NaCN and KCN
Which solution has the greatest ability to resist a change in pH (or buffering capacity)? a) 0.543 M NH3 and 0.555 M NH4 Clb) 0.087 M NH3 and 0.088 M NH4 Clc) 0.234 M NH3 and 0.100 M NH4 Cld) 0.100 M NH3 and 0.455 M NH4 Cle) They are all buffer solutions and would all have the same capacity.
The addition of hydrochloric acid and __________ to water produces a buffer solution.a) HC6H5Ob) NaOHc) NH3d) HNO3e) NaNO3
At a pH of 7.40, what is the ratio of the molar concentrations of CO  32− to HCO3−?Express your answer using two significant figures.
At a pH of 7.40, what is the ratio of the molar concentrations of HCO  3− to H2CO3?Express your answer using two significant figures.
The Ka values for nitrous acid (HNO2) and hypochlorous (HCIO) acid are 4.5 x 10 -4 and 3.0 x 10 -8 respectively.What other substance containing sodium would be needed to make the buffer? Express your answer as a chemical formula.
A certain aqueous HCNO solution has a pH of 2.17. If solid KCNO is added to the solution, will the pH increase, decrease, or remain the same? Assume that there is no volume change upon addition of KCNO.
Of the following, which is the best base to create a buffer with a pH = 8.0?a. Aniline, Kb = 4.3 x 10-10b. Ethylamine, Kb = 6.4 x 10-4c. Hydrazine, Kb = 1.3 x 10-6d. Pyridine, Kb = 1.7 x 10-9
Which pair of compounds will form a buffer in aqueous solution? a. HCl and NaOH b. NaCN and KCN c. HCN and HCl d. HCN and NaCN  e. NaCN and NaOH
Which of the following molar ratios is the correct equilibrium ratio of BASE: ACID for a solution made of aniline (Kb = 3.8 x 10-10) and anilinum nitrate where the pH is 4.80? 1. 1:2 2. 3:5 3. 7:2 4. 2:1 5. 5:3 6. 4:1 7. 9:1
Of the following solutions, which has the greatest buffering capacity?a. 0.100 M NH3 and 0.455 M NH4CIb. 0.087 M NH3 and 0.088 M NH4CIc. They are all buffer solutions and would all have the same capacity.d. 0.234 M NH3 and 0.100 M NH4CIe. 0.543 M NH3 and 0.555 M NH4CI
A 1.0 L buffer solution is 0.10 M in HF and 0.050 M in NaF. Which action destroys the buffer?(a) adding 0.050 mol of HCl(b) adding 0.050 mol of NaOH(c) adding 0.050 mol of NaF(d) none of the above
A buffer contains 0.10 mol of a weak acid and 0.20 mol of its conjugate base in 1.0 L of solution. Determine whether or not adding 0.020 mol of NaOH exceed the capacity of the buffer.
A buffer contains 0.10 mol of a weak acid and 0.20 mol of its conjugate base in 1.0 L of solution. Determine whether or not adding 0.020 mol of HCl exceed the capacity of the buffer.
A buffer contains 0.10 mol of a weak acid and 0.20 mol of its conjugate base in 1.0 L of solution. Determine whether or not adding 0.10 mol of NaOH exceed the capacity of the buffer.
A buffer contains 0.10 mol of a weak acid and 0.20 mol of its conjugate base in 1.0 L of solution. Determine whether or not adding 0.010 mol of HCl exceed the capacity of the buffer.
Which combination is the best choice to prepare a buffer with a pH of 9.0?a) NH3; NH4Cl (pKb for NH3 is 4.75)b) C5H5N; C5H5NHCl (pKb for C5H5N is 8.76)c) HNO2; NaNO2 (pKa for HNO2 is 3.33)d) HCHO2; NaCHO2 (pKa for HCHO2 is 3.74)
Buffers that are based on 3-morpholinopropanesulfonic acid (MOPS) are often used in RNA analysis. The useful pH range of a MOPS buffer is 6.5 to 7.9. Estimate the Ka of MOPS.
Calculate the pH after 0.010 mole of gaseous HCl is added to 250.0 mL of each of the following buffered solutions.a. 0.050 M NH3/0.15 M NH4Clb. 0.50 M NH3/1.50 M NH4ClDo the two original buffered solutions differ in their pH or their capacity? What advantage is there in having a buffer with a greater capacity?
Which of the following solutions is a good buffer system?a. 0.10M LiC2H3O2 and 0.10M HBrb. 0.10 M NH4+ and 0.10M HIc. 0.10 M LiOH and 0.10M KOHd. 0.10M HC2H3O2 and 0.10M LiC2H3O2
Consider the acids in Table 13‑2. Which acid would be the best choice for preparing a pH = 7.00 buffer? Explain how to make 1.0 L of this buffer.
Consider the bases in Table 13‑3. Which base would be the best choice for preparing a pH = 5.00 buffer? Explain how to make 1.0 L of this buffer.
Closely examine the figure below:Which image best represents the amount of OH- added to the buffer in part (b) of the figure?
The scenes below depict solutions of the same HA/A− buffer (HA is red and blue and A− is red; other ions and water molecules have been omitted for clarity).(a) Which solution has the greatest buffer capacity?
The scenes below depict solutions of the same HA/A− buffer (HA is red and blue and A− is red; other ions and water molecules have been omitted for clarity).(b) Explain how the pH ranges of the buffers compare.
The scenes below depict solutions of the same HA/A− buffer (HA is red and blue and A− is red; other ions and water molecules have been omitted for clarity).(c) Which solution can react with the largest amount of added strong acid?
The scenes below show three samples of a buffer consisting of HA and A− (HA is green and blue and A− is green; other ions and water are not shown).(a) Which buffer can react with the largest amount of added strong base?
The scenes below show three samples of a buffer consisting of HA and A− (HA is green and blue and A− is green; other ions and water are not shown).(b) Which buffer has the highest pH?
The scenes below show three samples of a buffer consisting of HA and A− (HA is green and blue and A− is green; other ions and water are not shown).(c) Which buffer has pH = pKa?
Which of the following buffer systems would be the best choice to create a buffer with pH exttip{pH}{pH}= 7.3? For the best system, calculate the ratio of the masses of the buffer components required to make the buffer.a. HC2H3O2/KC2H3O2b. HClO2/KClO2c. NH3/NH4Cld. HClO/KClO
Which of the following buffer systems would be the best choice to create a buffer with pH exttip{ m pH}{pH}= 9.00? For the best system, calculate the ratio of the masses of the buffer components required to make the buffer.a. HF/KFb. HNO2/KNO2c. NH3/NH4Cld. HClO/KClO
Explain why the pH does not change significantly when a small amount of an acid or a base is added to a solution that contains equal amounts of the acid H3PO4 and a salt of its conjugate base NaH2PO4.
Explain why the pH does not change significantly when a small amount of an acid or a base is added to a solution that contains equal amounts of the base NH3 and a salt of its conjugate acid NH4Cl.
A 500.0-mL buffer solution is 0.100 M in HNO2 and 0.150 M in KNO2. Determine whether or not 250 mg NaOH would exceed the capacity of the buffer to neutralize it.
A 500.0-mL buffer solution is 0.100 M in HNO2 and 0.150 M in KNO2. Determine whether or not 350 mg KOH would exceed the capacity of the buffer to neutralize it.
A 500.0-mL buffer solution is 0.100 M in HNO2 and 0.150 M in KNO2. Determine whether or not 1.25 g HBr would exceed the capacity of the buffer to neutralize it.
A 500.0-mL buffer solution is 0.100 M in HNO2 and 0.150 M in KNO2. Determine whether or not 1.35 g HI would exceed the capacity of the buffer to neutralize it.
A buffer consists of 0.22 M KHCO3 and 0.37 M K2CO3. Carbonic acid is a diprotic acid with Ka1 = 4.5×10−7 and Ka2 = 4.7×10−11.(a) Which Ka value is more important to this buffer?
A buffer consists of 0.50 M NaH2PO4 and 0.40 M Na2HPO4. Phosphoric acid is a triprotic acid (Ka1 = 7.2×10−3, Ka2 = 6.3×10−8, and Ka3 = 4.2×10−13).(a) Which Ka value is most important to this buffer?
A buffer consists of 0.50 M NaH2PO4 and 0.40 M Na2HPO4. Phosphoric acid is a triprotic acid (Ka1 = 7.2×10−3, Ka2 = 6.3×10−8, and Ka3 = 4.2×10−13).(b) What is the buffer pH?
Which acid in the following table is most appropriate for preparation of a buffer solution with a pH of 3.1? Explain your choice.
Which acid in the following table is most appropriate for preparation of a buffer solution with a pH of 3.7? Explain your choice.
Which base in the following table is most appropriate for preparation of a buffer solution with a pH of 10.65? Explain your choice.
Amino acids [general formula NH 2CH(R)COOH] can be considered polyprotic acids. In many cases, the R group contains additional amine and carboxyl groups.(c) The R group of lysine is —CH2CH2CH2CH2NH2 (pKb = 3.47). Draw the structure of lysine at pH 1, physiological pH (∼7), and pH 13.
Amino acids [general formula NH 2CH(R)COOH] can be considered polyprotic acids. In many cases, the R group contains additional amine and carboxyl groups.(d) The R group of glutamic acid is —CH2CH2COOH (pKa = 4.07). Of the forms of glutamic acid that are shown below, which predominates at (1) pH 1, (2) physiological pH (∼7), and (3) pH 13?
Which solution would come closest to making a pH 7 buffer? (Reference data for phosphoric acid, H3PO4: pKa1 = 2.2, pKa2 = 7.2, pKa3 = 12.2) a. a solution containing equal amounts of Na2HPO4 and Na3PO4 b. a solution containing equal amounts of H3PO4 and NaH2PO4 c. a solution containing equal amounts of NaH2PO4 and Na2HPO4 d. a solution of Na2HPO4 e. a solution of NaH2PO4    
Choose specific acid-base conjugate pairs to make the following buffers: (a) pH ≈ 4.5. (See Appendix C.)
Choose specific acid-base conjugate pairs to make the following buffers: (b) pH ≈ 7.0. (See Appendix C.)
Choose specific acid-base conjugate pairs to make the following buffers: (a) [H3O+] ≈ 1 × 10−9 M.(See Appendix C.)
A certain buffer is made by dissolving NaHCO3 and Na2CO3 in some water. Write equations to show how this buffer neutralizes added H+ and OH -.
Consider the following acids and bases:Choose substances from the following list that would be the best choice to prepare a pH = 9.0 buffer solution.a. HCO2Hb. HOBrc. KHCO2d. HONH3NO3e. (C2H5)2NHf. (C2H5)2NH2Clg. HONH2h. NaOBr
Choose specific acid-base conjugate pairs to make the following buffers: (b) [OH−] ≈ 3 × 10−5 M.(See Appendix C.)
Consider a buffered solution containing CH3NH3Cl and CH3NH2. Which of the following statements concerning this solution is(are) true? (Ka for CH3NH3+ = 2.3 x 10 -11.)a. A solution consisting of 0.10 M CH 3NH3Cl and 0.10 M CH3NH2 would have a higher buffering capacity than one containing 1.0 M CH3NH3Cl and 1.0 M CH3NH2.b. If [CH3NH2] > [CH3NH3+], then the pH is larger than the pK a value.c. Adding more [CH3NH3Cl] to the initial buffer solution will decrease the pH.d. If [CH3NH2] < [CH3NH3+], then pH < 3.36.e. If [CH3NH2] = [CH3NH3+], then pH = 10.64.
Choose specific acid-base conjugate pairs to make the following buffers: (a) pH ≈ 3.5. (See Appendix C.)
Choose specific acid-base conjugate pairs to make the following buffers: (b) pH ≈ 5.5. (See Appendix C.)
A buffer is prepared by dissolving HONH2 and HONH3NO3 in some water. Write equations to show how this buffer neutralizes added H+ and OH -.
Choose specific acid-base conjugate pairs to make the following buffers: (a) [OH−] ≈ 1 × 10−6 M. (See Appendix C.)
Choose specific acid-base conjugate pairs to make the following buffers: (b) [H3O+] ≈ 4 × 10−4 M. (See Appendix C.)
Tris(hydroxymethyl)aminomethane, commonly called TRIS or Trizma, is often used as a buffer in biochemical studies. Its buffering range is pH 7 to 9, and Kb is 1.19 x 10-6 for the aqueous reactiona. What is the optimal pH for TRIS buffers?
Which base in the following table is most appropriate for preparation of a buffer solution with a pH of 9.20? Explain your choice.
Amino acids are the building blocks for all proteins in our bodies. A structure for the amino acid alanine isAll amino acids have at least two functional groups with acidic or basic properties. In alanine, the carboxylic acid group has Ka = 4.5 x 10 -3 and the amino group has K b = 7.4 x 10 -5. Because of the two groups with acidic or basic properties, three different charged ions of alanine are possible when alanine is dissolved in water. Which of these ions would predominate in a solution with [H+] = 1.0 M? In a solution with [OH -] = 1.0 M?
Which of the following solutions shows the least change in pH upon the addition of acid or base? Explain.a. 0.100 M propanoic acid (HC3H5O2, Ka = 1.3 x 10-5)b. 0.100 M sodium propanoate (NaC3H5O2)c. pure H2Od. a mixture containing 0.100 M HC3H5O2 and 0.100 M NaC3H5O2
Phosphate buffers are important in regulating the pH of intracellular fluids at pH values generally between 7.1 and 7.2. b. Why is a buffer composed of H3PO4 to H2PO4- ineffective in buffering the pH of intracellular fluid?H3PO4 (aq) ⇌ H2PO4- (aq) + H+ (aq)            K a = 7.5 x 10 -3
Benzoic acid C6H5COOH is a weak acid with K a = 6.3 x 10-5 C6H5CO2H (aq) + H2O (l) ⇌ H3O+ (aq) + C6H5CO2- (aq) a) Calculate the pH of a 0.150 M benzoic acid solution. Show all calulations. b) Suppose 1.44g of sodium benzoate, Na+C6H5COO-, is added to 100.0 mL of the 0.150 M benzioic acid solution. Calculate the pH of the resulting buffer solution assuming the volume of the solution does not change on addition of the solid.
Rainwater is slightly acidic due to dissolved CO 2. Use the following data to calculate the pH of unpolluted rainwater at 25°C: vol % in air of CO2 = 0.040 vol %; solubility of CO 2 in pure water at 25°C and 1 atm = 88 mL CO2/100. mL H2O; Ka1 of H2CO3 = 4.5 × 10−7.
Seawater at the surface has a pH of about 8.5. (a) Which of the following species has the highest concentration at this pH: H 2CO3; HCO3−; CO32−? Explain.
Seawater at the surface has a pH of about 8.5. (b) What are the concentration ratios [CO32−]/[HCO3−] and [HCO3−]/[H2CO3] at this pH?
Seawater at the surface has a pH of about 8.5. (a) Which of the following species has the highest concentration at this pH: H2CO3; HCO3−; CO32−? Explain.(b) What are the concentration ratios [CO32−]/[HCO3−] and [HCO3−]/[H2CO3] at this pH?(c) In the deep sea, light levels are low, and the pH is around 7.5. Suggest a reason for the lower pH at the greater ocean depth. (Hint: Consider the presence or absence of plant and animal life and the effects on carbon dioxide concentrations.)
Use information from Appendix D in the textbook to calculate the pH of the following solutions.Calculate the pH of a solution that is 0.065 M in potassium propionate (C2 H5 COOK or KC3H5O2) and 0.090 M in propionic acid (C2 H5 COOH or HC3H5O2).
Use information from Appendix D in the textbook to calculate the pH of the following solutions.Calculate the pH of a solution that is 0.080 M in trimethylamine, (CH3)3N, and 0.12 M in trimethylammonium chloride, ((CH3)3NHCl).
Use information from Appendix D in the textbook to calculate the pH of the following solutions.Calculate the pH of a solution that is made by mixing 50.0 mL of 0.16 M acetic acid and 50.0 mL of 0.22 M sodium acetate.
Use the Henderson-Hasselbalch equation to calculate the pH of each solution: a solution that is 0.185 M in HC2H3O2 and 0.115 M in KC2H3O2
If the pKa of HCHO2 is 3.74 and the pH of an HCHO 2/NaCHO2 solution is 3.89, which of the following is true? A) [HCHO2] < [NaCHO2] B) [HCHO2] > [NaCHO2] C) [HCHO2] = [NaCHO2] D) [HCHO2] >> [NaCHO2] E) It is not possible to make a buffer of this pH from HCHO 2 and NaCHO2
Use the Henderson-Hasselbalch equation to calculate the pH of each solution: a solution that is 0.225 M in CH3NH2 and 0.120 M in CH3NH3Br
Calculate the pH of the solution that results from each of the following mixtures: 160.0 mL of 0.26 M HF with 230.0 mL of 0.32 M  NaF
Calculate the pH of the solution that results from each of the following mixtures: 180.0 mL of 0.12 M C2H5NH2 with 280.0 mL of 0.22 M C2H5NH3Cl
A 120.0 -mL buffer solution is 0.110 M in NH3 and 0.135 M in NH4Br. What mass of HCl can this buffer neutralize before the pH falls below 9.00?        
Calculate the percent ionization of 0.0080 M butanoic acid in a solution containing 0.080 M sodium butanoate.
The pKa of formic acid (HCOOH) is 3.74, a monoprotic weak acid. A 1.0 L sample of a buffer with a pH of 4.5 is combined with 0.09 moles of NaOH. What is the new pH of the solution? The ratio of HCOO- to HCOOH is 0.86 M to 0.15 M.
A 120.0-mL buffer solution is 0.110 M in NH3 and 0.135 M in NH4Br. If the same volume of the buffer were 0.265 M in NH3 and 0.400 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00?        
Calculate the percent ionization of 0.130 M lactic acid in a solution containing 8.0×10−3  M sodium lactate.
Use information from Appendix D in the textbook to calculate the pH of the following solutions.Calculate the pH of a solution that is 0.260 M in sodium formate (HCOONa) and 0.120 M in formic acid (HCOOH).
A 160.0-mL solution contains 2.15 g of sodium benzoate and 2.50 g of benzoic acid. Calculate the pH of the solution.
Use information from Appendix D in the textbook to calculate the pH of the following solutions.Calculate the pH of a solution that is 0.530 M in pyridine (C5H5N) and 0.460 M in pyridinium chloride (C5H5NHCl).
A solution is made by combining 15.0 mL of 18.0 M acetic acid with 5.56 g of sodium acetate and diluting to a total volume of 1.50 L. Calculate the pH of the solution.
Use information from Appendix D in the textbook to calculate the pH of the following solutions.Calculate the pH of a solution that is made by combining 55 mL of 0.060 M hydrofluoric acid with 125 mL of 0.120 M sodium fluoride.
A buffer is created by combining 160.0 mL of 0.30 M HCHO2 with 80.0 mL of 0.25 M NaOH. Determine the pH of the buffer.
A buffer is created by combining 3.60 g of NH3 with 4.82 g of HCl and diluting to a total volume of 850.0 mL. Determine the pH of the buffer.
A 1.0-L buffer solution initially contains 0.30 mol of NH3 and 0.30 mol of NH4Cl. In order to adjust the buffer pH to 8.80, should you add NaOH or HCl to the buffer mixture?
If the pH of a buffer solution is equal to the pKa of the acid in the buffer, what does this tell you about the relative concentrations of the acid and conjugate base forms of the buffer components?
A 260.0-mL buffer solution initially contains 3.0×10−2 M of HCHO2 and 3.0×10−2 M of NaCHO2. In order to adjust the buffer pH to 4.20, should you add NaOH or HCl to the buffer mixture?
A 260.0 -mL buffer solution initially contains 3.0×10−2 M of HCHO2 and 3.0×10−2 M of NaCHO2. In order to adjust the buffer pH to 4.10, should you add NaOH or HCl to the buffer mixture? What mass of the correct reagent should you add?
A 0.25-mol sample of a weak acid with an unknown pKa was combined with 12.0 mL of 3.10 M KOH and the resulting solution was diluted to 1.500 L. The measured pH of the solution was 3.90. What is the pKa of the weak acid?
A 5.60-g sample of a weak acid with Ka = 1.3 x 10–4 was combined with 5.10 mL of 6.10 M NaOH and the resulting solution was diluted to 750 mL. The measured pH of the solution was 4.25. What is the molar mass of the weak acid?
Calculate the pH of a buffer that is 0.205 M in NaHCO3 and 0.285 M in Na2CO3.
Calculate the pH of a solution formed by mixing 65 mL of a solution that is 0.26 M in NaHCO3 with 75 mL of a solution that is 0.21 M in Na2CO3.
A buffer solution contains 0.11 mol of acetic acid and 0.14 mol of sodium acetate in 1.00 L.What is the pH of this buffer?
A buffer solution contains 0.11 mol of acetic acid and 0.14 mol of sodium acetate in 1.00 L.What is the pH of the buffer after the addition of 0.03 mol of KOH?
A buffer solution contains 0.11 mol of acetic acid and 0.14 mol of sodium acetate in 1.00 L.What is the pH of the buffer after the addition of 0.03 mol of HNO3?
Calculate the number of grams of ammonium chloride that must be added to 2.00 L of a 0.500 M ammonia solution to obtain a buffer of pH = 9.20. Assume the volume of the solution does not change as the solid is added. exttip{K_{ m b}}{K_b} for ammonia is 1.80 10-5.
Aniline, abbreviated ɸNH2, where ɸ is C6H5, is an important organic base used in the manufacture of dyes. It has Kb = 4.3 x 10-10. In a certain manufacturing process it is necessary to keep the concentration of ɸNH3+ (aniline’s conjugate acid, the anilinium ion) below 1.0 x 10-9 M in a solution that is 0.10 M in aniline. Find the concentration of NaOH required for this process.
The Kb of hydroxylamine, NH2 OH, is 1.10 x 10–8. A buffer solution is prepared by mixing 120 mL of a 0.37 M hydroxylamine solution with 60 mL of a 0.27 M HCl solution. Find the pH of the resulting solution.
A buffer contains the weak acid HA and its conjugate base A–. The weak acid has a pKa of 4.82 and the buffer has a pH of 4.25. Which statement is true of the relative concentrations of the weak acid and conjugate base in the buffer?(a) [HA] > [A–](b) [HA] < [A–](c) [HA] = [A–]
What relative masses of dimethyl amine and dimethyl ammonium chloride do you need to prepare a buffer solution of pH exttip{ m pH}{pH}= 10.35?
A buffer, consisting of H2PO4- and HPO42-, helps control the pH of physiological fluids. Many carbonated soft drinks also use this buffer system.What is the pH of a soft drink in which the major buffer ingredients are 6.6 g of NaH2PO4 and 8.3 g of Na2HPO4 per 355 mL of solution?
You are asked to prepare 2.6 L of a HCN/NaCN buffer that has a pH of 9.66 and an osmotic pressure of 1.51 atm at 298 K. What masses of HCN and NaCN should you use to prepare the buffer? (Assume complete dissociation of NaCN.)
A buffer contains equal amounts of a weak acid and its conjugate base and has a pH of 5.25. Which would be a reasonable value of buffer pH after the addition of a small amount of acid?(a) 4.15(b) 5.15(c) 5.35(d) 6.35
What amount of solid NaOH must be added to 1.0 L of a 0.13 M H2CO3 solution to produce a solution with [H+] = 3.3×10−11 M? There is no significant volume change as the result of the addition of the solid.
A buffer is prepared by adding 11.00 g of ammonium chloride (NH4Cl) to 250 mL of a solution 1.00 M in NH3.What is the pH of this buffer?
What amount of HCl gas must be added to 1.00 L of a buffer solution that contains [acetic acid] = 2.0 M and [acetate] = 1.0 M in order to produce a solution with pH exttip{ m pH}{pH}= 3.96?
Calculate the pH of each of the following solutions.d. a mixture containing 0.100 M HC3H5O2 and 0.100 M NaC3H5O2
A buffer contains 0.16 mol of propionic acid (C2H5COOH) and 0.22 mol of sodium propionate (C2H5COONa) in 1.20 L.What is the pH of this buffer?
A buffer contains 0.16 mol of propionic acid (C2H5COOH) and 0.22 mol of sodium propionate (C2H5COONa) in 1.20 L.What is the pH of the buffer after the addition of 0.02 mol of NaOH?
A buffer contains 0.16 mol of propionic acid (C2H5COOH) and 0.22 mol of sodium propionate (C2H5COONa) in 1.20 L.What is the pH of the buffer after the addition of 0.02 mol of HI?
Calculate the pH of each of the following solutions.d. a mixture containing 0.100 M HONH2 and 0.100 M HONH3Cl
Calculate the pH of a solution that is 1.00 M HNO2 and 1.00 M NaNO2.
Calculate the pH of a buffer solution that is 0.260 M in HC2H3O2 and 0.160 M in NaC2H3O2. (Ka for HC2H3O2 is 1.8 x 10–5)
Calculate the pH of a solution that is 0.60 M HF and 1.00 M KF.
A 1.0-L buffer solution contains 0.100 mol HC2H3O2 and 0.100 mol NaC2H3O2. The value of Ka for HC2H3O2 is 1.8 x 10–5. Calculate the pH of the solution, upon addition of 0.055 mol of NaOH to the original buffer.        
Calculate the pH after 0.10 mole of NaOH is added to 1.00 L of a solution that is 1.00 M HNO2 and 1.00 M NaNO2, and calculate the pH after 0.20 mole of HCl is added to 1.00 L of a solution that is 1.00 M HNO2 and 1.00 M NaNO2.
Calculate the pH after 0.10 mole of NaOH is added to 1.00 L of a solution that is 0.60 M HF and 1.00 M KF, and calculate the pH after 0.20 mole of HCl is added to 1.00 L of a solution that is 0.60 M HF and 1.00 M KF.
You are asked to prepare a pH = 4.00 buffer starting from 1.50 L of 0.0200 M solution of benzoic acid (C6H5COOH) and an excess of sodium benzoate (C6H5COONa).What is the pH of the benzoic acid solution prior to adding sodium benzoate?
Calculate the pH of each of the following buffered solutions.a. 0.10 M acetic acid/0.25 M sodium acetate
You are asked to prepare a pH = 4.00 buffer starting from 1.50 L of 0.0200 M solution of benzoic acid (C6H5COOH) and an excess of sodium benzoate (C6H5COONa).How many grams of sodium benzoate should be added to prepare the buffer? Neglect the small volume change that occurs when the sodium benzoate is added.
Calculate the pH of each of the following buffered solutions.b. 0.25 M acetic acid/0.10 M sodium acetate
A formic acid solution has a pH of 3.25. Which of these substances will raise the pH of the solution upon addition?a. HClb. NaBrc. NaCHO2d. KCl
What is the pH of a buffer that is 0.120 M in formic acid (HCHO2) and 0.080 M in potassium formate (KCHO2)? For formic acid, Ka = 1.8 x 10–4.
Calculate the pH of each of the following buffered solutions.c. 0.080 M acetic acid/0.20 M sodium acetate
A buffer with a pH of 9.85 contains CH3NH2 and CH3NH3Cl in water. What can you conclude about the relative concentrations of CH3NH2 and CH3NH3Cl in this buffer? For CH3NH2, pKb = 3.36.
Calculate the pH of the buffer that results from mixing 55.1 mL of a 0.351 M solution of HCHO2 and 15.1 mL of a 0.626 M solution of NaCHO2. The Ka value for HCHO2 is 1.8 x 10–4.
Calculate the pH of each of the following buffered solutions.d. 0.20 M acetic acid/0.080 M sodium acetate
A 500.0 mL buffer solution is 0.10 M in benzoic acid and 0.10 M in sodium benzoate and has an initial pH of 4.19. What is the pH of the buffer upon addition of 0.010 mol of NaOH?
A 1.0-L buffer solution contains 0.100 mol HC2H3O2 and 0.100 mol NaC2H3O2. The value of Ka for HC2H3O2 is 1.8 x 10–5. Calculate the pH of the solution upon addition of 50.1 mL of 1.00 MHCl to the original buffer.
Calculate the pH of each of the following buffered solutions.a. 0.50 M C2H5NH2/0.25 M C2H5NH3Cl
Solve an equilibrium problem (using an ICE table) to calculate the pH of each solution:a solution that is 0.185 M in HC2H3O2 and 0.115 M in KC2H3O2
Calculate the pH of each of the following buffered solutions.b. 0.25 M C2H5NH2/0.50 M C2H5NH3Cl
Solve an equilibrium problem (using an ICE table) to calculate the pH of each solution:a solution that is 0.225 M in CH3NH2 and 0.120 M in CH3NH3Br
Calculate the pH of each of the following buffered solutions.c. 0.50 M C2H5NH2/0.50 M C2H5NH3Cl
Calculate the pH of a buffered solution prepared by dissolving 21.5 g benzoic acid (HC7H5O2) and 37.7 g sodium benzoate in 200.0 mL of solution.
A buffered solution is made by adding 50.0 g NH4Cl to 1.00 L of a 0.75-M solution of NH3. Calculate the pH of the final solution. (Assume no volume change.)
Calculate the pH after 0.010 mole of gaseous HCl is added to 250.0 mL of each of the following buffered solutions.a. 0.050 M NH3/0.15 M NH4Cl
Scenes A to D represent tiny portions of 0.10 M aqueous solutions of a weak acid HA (red and blue; Ka = 4.5×10−5), its conjugate base A−(red), or a mixture of the two (only these two species are shown):(b) What is the pH of each solution?
Solve an equilibrium problem (using an ICE table) to calculate the pH of each of the following solutions. a mixture that is 0.14 M in HF and 0.14 M in NaF (Ka =6.8 x 10–4)
An aqueous solution contains dissolved C6H5NH3Cl and C6H5NH2. The concentration of C6H5NH2 is 0.50 M and pH is 4.20.a. Calculate the concentration of C6H5NH3+ in this buffer solution.
An aqueous solution contains dissolved C6H5NH3Cl and C6H5NH2. The concentration of C6H5NH2 is 0.50 M and pH is 4.20.b. Calculate the pH after 4.0 g NaOH(s) is added to 1.0 L of this solution. (Neglect any volume change.)
Solve an equilibrium problem (using an ICE table) to calculate the pH of each of the following solutions.a mixture that is 0.16 M in CH3NH2 and 0.16 M in CH3NH3Cl
Calculate the mass of sodium acetate that must be added to 500.0 mL of 0.200 M acetic acid to form a pH = 5.00 buffer solution.
What volumes of 0.50 M HNO2 and 0.50 M NaNO2 must be mixed to prepare 1.00 L of a solution buffered at pH = 3.55?
Calculate the pH of a buffer solution that is 0.251 M in HCN and 0.170 M in KCN. For HCN, Ka = 4.9×10−10 (pKa = 9.31).
Consider a solution that contains both C5H5N and C5H5NHNO3. Calculate the ratio [C5H5N] / [C5H5NH+] if the solution has the following pH values:a. pH = 4.50 
Ammonium (NH4+) is a weak acid with a pK a of 9.26. The dissociation is:NH4+ ⇌ NH3 + H+Calculate the mass of ammonium added to 1 L of water in order to obtain a pH of 4 at equilibrium. 
Consider a solution that contains both C5H5N and C5H5NHNO3. Calculate the ratio [C5H5N] / [C5H5NH+] if the solution has the following pH values:b. pH = 5.00
Consider a solution that contains both C5H5N and C5H5NHNO3. Calculate the ratio [C5H5N] / [C5H5NH+] if the solution has the following pH values:c. pH = 5.23
Use the Henderson–Hasselbalch equation to calculate the pH of each solution:a solution that contains 1.26% C2H5NH2 by mass and 1.26% C2H5NH3Br by mass
Use the Henderson–Hasselbalch equation to calculate the pH of each solution:a solution that is 13.0 g of HC2H3O2 and 13.0 g of NaC2H3O2 in 150.0 mL of solution
Consider a solution that contains both C5H5N and C5H5NHNO3. Calculate the ratio [C5H5N] / [C5H5NH+] if the solution has the following pH values:d. pH = 5.50
Calculate the ratio [NH3] / [NH4+] in ammonia/ammonium chloride buffered solutions with the following pH values:a. pH = 9.00
Use the Henderson–Hasselbalch equation to calculate the pH of each solution:a solution that contains 0.705% C5H5N by mass and 0.905% C5H5NHCl by mass
Calculate the ratio [NH3] / [NH4+] in ammonia/ammonium chloride buffered solutions with the following pH values:b. pH = 8.80
Calculate the ratio [NH3] / [NH4+] in ammonia/ammonium chloride buffered solutions with the following pH values:c. pH = 10.00
Calculate the ratio [NH3] / [NH4+] in ammonia/ammonium chloride buffered solutions with the following pH values:d. pH = 9.60
Calculate the pH of the solution that results from each of the following mixtures.130.0 mL of 0.12 M NH3 with 260.0 mL of 0.12 M NH4Cl
Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in NH4Cl. For ammonia, pKb= 4.75. Calculate the pH of 1.0 L upon addition of 0.110 mol of solid NaOH to the original buffer solution.
Carbonate buffers are important in regulating the pH of blood at 7.40. If the carbonic acid concentration in a sample of blood is 0.0012 M, determine the bicarbonate ion concentration required to buffer the pH of blood at pH 5 7.40. H2CO3 (aq) ⇌ HCO3- (aq) + H+ (aq)        K a = 4.3 x 10 -7
Calculate the ratio of NaF to HF required to create a buffer with pH exttip{pH}{pH}= 4.05.
When a person exercises, muscle contractions produce lactic acid. Moderate increases in lactic acid can be handled by the blood buffers without decreasing the pH of blood. However, excessive amounts of lactic acid can overload the blood buffer system, resulting in a lowering of the blood pH. A condition called acidosis is diagnosed if the blood pH falls to 7.35 or lower. Assume the primary blood buffer system is the carbonate buffer system described in Exercise 45. Calculate what happens to the [H2CO3] / [HCO3-] ratio in blood when the pH decreases from 7.40 to 7.35.
What volumes of 0.200 M HCOOH and 2.00 M NaOH would make 500. mL of a buffer with the same pH as a buffer made from 475 mL of 0.200 M benzoic acid and 25 mL of 2.00 M NaOH?
Calculate the ratio of CH3NH2 to CH3NH3Cl required to create a buffer with pH exttip{pH}{pH}= 10.22.
You may want to refernce(Pages 792 - 794)Section 17.3 while completing this problem.If you have 500 mL of a 0.10 M solution of hypochlorous acid (HClO, pKa = 7.54), what mass of the corresponding sodium salt of the conjugate base do you need to make the buffer with a pH of 7.38 (assuming no change in volume)?
A microbiologist is preparing a medium on which to culture E. coli bacteria. She buffers the medium at pH 7.00 to minimize the effect of acid-producing fermentation. What volumes of equimolar aqueous solutions of K2HPO4 and KH2PO4 must she combine to make 100. mL of the pH 7.00 buffer?
What mass of ammonium chloride should be added to 2.60 L of a 0.160 M NH3 in order to obtain a buffer with a pH of 9.60?       
Calculate the pH of a solution that is 0.40 M H 2NNH2 and 0.80 M H2NNH3NO3. In order for this buffer to have pH = pKa, would you add HCl or NaOH? What quantity (moles) of which reagent would you add to 1.0 L of the original buffer so that the resulting solution has pH = pKa?
A 260.0 mL buffer solution is 0.260 M in acetic acid and 0.260 M in sodium acetate. What is the initial pH of this solution?
Calculate the pH of a solution that is 0.20 M HOCl and 0.90 M KOCl. In order for this buffer to have pH = pKa, would you add HCl or NaOH? What quantity (moles) of which reagent would you add to 1.0 L of the original buffer so that the resulting solution has pH = pKa?
As an FDA physiologist, you need 0.700 L of formic acid– formate buffer with a pH of 3.74.(a) What is the required buffercomponent concentration ratio?
A 260.0 mL buffer solution is 0.260 M in acetic acid and 0.260 M in sodium acetate. What is the pH after addition of 0.0150 mol of HCl?
Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in NH4Cl. For ammonia, pKb= 4.75. Calculate the pH of 1.0 L of the solution, upon addition of 30.00 mL of 1.0 M HCl to the original buffer solution.
A 260.0 mL buffer solution is 0.260 M in acetic acid and 0.260 M in sodium acetate. What is the pH after addition of 0.0150 mol of NaOH?
As an FDA physiologist, you need 0.700 L of formic acid– formate buffer with a pH of 3.74.(b) How do you prepare this solution from stock solutions of 1.0 M HCOOH and 1.0 M NaOH?
A 100.0-mL buffer solution is 0.175 M in HClO and 0.150 M in NaClO. What is the initial pH of this solution?
What quantity (moles) of NaOH must be added to 1.0 L of 2.0 M HC2H3O2 to produce a solution buffered at each pH?a. pH = pKa
A 100.0-mL buffer solution is 0.175 M in HClO and 0.150 M in NaClO. What is the pH after addition of 150.0 mg of HBr?
What quantity (moles) of NaOH must be added to 1.0 L of 2.0 M HC2H3O2 to produce a solution buffered at each pH?b. pH = 4.00
A 100.0-mL buffer solution is 0.175 M in HClO and 0.150 M in NaClO. What is the pH after addition of 85.0 mg of NaOH?
What quantity (moles) of NaOH must be added to 1.0 L of 2.0 M HC2H3O2 to produce a solution buffered at each pH?b. pH = 5.00
Calculate the number of moles of HCl(g) that must be added to 1.0 L of 1.0 M NaC2H3O2 to produce a solution buffered at each pH.a. pH = pKa 
For 510.0 mL of a buffer solution that is 0.150 M in HC2H3O2 and 0.135 M in NaC2H3O2, calculate the initial pH and the final pH after adding 0.020 mol of HCl.
Calculate the number of moles of HCl(g) that must be added to 1.0 L of 1.0 M NaC2H3O2 to produce a solution buffered at each pH.b. pH = 4.20
For 510.0 mL of a buffer solution that is 0.170 M in CH3CH2NH2 and 0.155 M in CH3CH2NH3Cl, calculate the initial pH and the final pH after adding 0.020 mol of HCl.
Calculate the number of moles of HCl(g) that must be added to 1.0 L of 1.0 M NaC2H3O2 to produce a solution buffered at each pH.c. pH = 5.00
As an FDA physiologist, you need 0.700 L of formic acid– formate buffer with a pH of 3.74.(c) What is the final concentration of HCOOH in this solution?
For 260.0 mL of a buffer solution that is 0.225 M in HCHO2 and 0.300 M in KCHO2, calculate the initial pH and the final pH after adding 0.0200 mol of NaOH (Ka = 1.8 x 10–4).
A 360.0-mL buffer solution is 0.160 M in HF and 0.160 M in NaF. What mass of NaOH can this buffer neutralize before the pH rises above 4.00?
For 260.0 mL of a buffer solution that is 0.2922 M in CH3CH2NH2 and 0.2677 M in CH3CH2NH3Cl, calculate the initial pH and the final pH after adding 0.0200 mol of NaOH (Kb = 5.6 x 10–4).
A 360.0 -mL buffer solution is 0.160 M in HF and 0.160 M in NaF. If the same volume of the buffer were 0.360 M in HF and 0.360 M in NaF, what mass of NaOH could be handled before the pH rises above 4.00?
Blood is buffered by carbonic acid and the bicarbonate ion. Normal blood plasma is 0.024 M in HCO3– and 0.0012 M H2CO3 (pKa1 for H2CO3 at body temperature is 6.1). What is the pH of blood plasma?
Blood is buffered by carbonic acid and the bicarbonate ion. Normal blood plasma is 0.024 M in HCO3– and 0.0012 M H2CO3 (pKa1 for H2 CO3 at body temperature is 6.1). If the volume of blood in a normal adult is 5.0 L, what mass of HCl could be neutralized by the buffering system in blood before the pH fell below 7.0 (which would result in death)?
What are the [H3O+] and the pH of a propanoic acid– propanoate buffer that consists of 0.35 M CH3CH2COONa and 0.15 M CH3CH2COOH (Ka of propanoic acid = 1.3×10−5)?
Blood is buffered by carbonic acid and the bicarbonate ion. Normal blood plasma is 0.024 M in HCO3– and 0.0012 M H2CO3 (pKa1 for H2 CO3 at body temperature is 6.1). Given the volume from part B, what mass of NaOH could be neutralized before the pH rose above 7.8?
What are the [H3O+] and the pH of a benzoic acid–benzoate buffer that consists of 0.33 M C6H5COOH and 0.28 M C6H5COONa (Ka of benzoic acid = 6.3×10−5)?
The fluids within cells are buffered by H2PO4– and HPO42–. Calculate the ratio of H2PO4– to HPO42– required to maintain a pH of 7.1 within a cell.
What are the [H3O+] and the pH of a buffer that consists of 0.55 M HNO2 and 0.75 M KNO2 (Ka of HNO2 = 7.1×10−4)?
What are the [H3O+] and the pH of a buffer that consists of 0.20 M HF and 0.25 M KF (Ka of HF = 6.8×10−4)?
Find the pH of a buffer that consists of 0.45 M HCOOH and 0.63 M HCOONa (pKa of HCOOH = 3.74).
Find the pH of a buffer that consists of 0.95 M HBrO and 0.68 M KBrO (pKa of HBrO = 8.64).
What is [H3O+] in a solution of 0.25 M CH 3CO2H and 0.030 M NaCH3CO2? CH3 CO2 H(aq) + H2 O(l) ⇌ H3 O+(aq) + CH3 CO2 −(aq)      Ka = 1.8 × 10−5
What is [H3O+] in a solution of 0.075 M HNO 2 and 0.030 M NaNO 2?HNO2(aq) + H2 O(l) ⇌ H3 O+(aq) + NO2 −(aq)    Ka = 4.5 × 10−5
What is [OH−] in a solution of 0.125 M CH 3NH2 and 0.130 M CH3NH3Cl?CH3 NH2(aq) + H2 O(l) ⇌ CH3 NH3 +(aq) + OH−(aq)      K b = 4.4 × 10−4
What is [OH−] in a solution of 1.25 M NH 3 and 0.78 M NH4NO3?NH3(aq) + H2 O(l) ⇌ NH4 +(aq) + OH−(aq)     Kb = 1.8 × 10−5
A 1.0-L buffer solution is 0.125 M in HNO2 and 0.175 M in NaNO2. Determine the concentrations of HNO2 and NaNO2 after addition of 1.6 g HCl.
What concentration of NH4NO3 is required to make [OH−] = 1.0 × 10−5 in a 0.200-M solution of NH3?
A 1.0-L buffer solution is 0.125 M in HNO2 and 0.175 M in NaNO2. Determine the concentrations of HNO2 and NaNO2 after addition of 1.6 g NaOH.
What concentration of NaF is required to make [H 3O+] = 2.3 × 10−4 in a 0.300-M solution of HF?
A 1.0-L buffer solution is 0.125 M in HNO2 and 0.175 M in NaNO2. Determine the concentrations of HNO2 and NaNO2 after addition of 1.6 g HI.
Water flowing through pipes of carbon steel must be kept at pH 5 or greater to limit corrosion. If an 8.0 × 103 lb/h water stream contains 10 ppm sulfuric acid and 0.015% acetic acid, how many pounds per hour of sodium acetate trihydrate must be added to maintain that pH?
Find the pH of a buffer that consists of 1.3 M sodium phenolate (C6H5ONa) and 1.2 M phenol (C6H5OH) (pKa of phenol = 10.00).
Find the pH of a buffer that consists of 0.12 M boric acid (H3BO3) and 0.82 M sodium borate (NaH2BO3) (pKa of boric acid = 9.24).
Find the pH of a buffer that consists of 0.50 M methylamine (CH3NH2) and 0.60 M CH3NH3Cl (pKb of CH3NH2 = 3.35).
Phosphate systems form essential buffers in organisms. Calculate the pH of a buffer made by dissolving 0.80 mol of NaOH in 0.50 L of 1.0 M H3PO4.
The pKa of acetic acid CH3COOH is 4.76. A buffer solution contains CH3COOH and CH3COONa and has a pH of 4.76 and a total acetate concentration (acid and base forms) of 0.400 M. What is the concentration of CH3COOH?
What will be the pH of a buffer solution prepared from 0.20 mol NH 3, 0.40 mol NH4NO3, and just enough water to give 1.00 L of solution?
Calculate the pH of a buffer solution prepared from 0.155 mol of phosphoric acid, 0.250 mole of KH2PO4, and enough water to make 0.500 L of solution.
A buffer consists of 0.22 M KHCO3 and 0.37 M K2CO3. Carbonic acid is a diprotic acid with Ka1 = 4.5×10−7 and Ka2 = 4.7×10−11.(b) What is the buffer pH?
It is possible to detect NH3 gas over 10−2 M NH3. To what pH must 0.15 M NH 4Cl be raised to form detectable NH3? 
How much solid NaCH3CO2•3H2O must be added to 0.300 L of a 0.50-M acetic acid solution to give a buffer with a pH of 5.00?
You need to produce a buffer solution that has a pH of 5.21. You already have a solution that contains 10. mmol (millimoles) of acetic acid. How many millimoles of acetate (the conjugate base of acetic acid) will you need to add to this solution? The pKa of acetic acid is 4.74. Express your answer numerically in millimoles.
What mass of NH 4Cl must be added to 0.750 L of a 0.100-M solution of NH 3 to give a buffer solution with a pH of 9.26?
A buffer solution is prepared from equal volumes of 0.200 M acetic acid and 0.600 M sodium acetate. Use 1.80 × 10−5 as Ka for acetic acid.(a) What is the pH of the solution?
A buffer solution is prepared from equal volumes of 0.200 M acetic acid and 0.600 M sodium acetate. Use 1.80 × 10−5 as Ka for acetic acid.(b) Is the solution acidic or basic?
A buffer solution is prepared from equal volumes of 0.200 M acetic acid and 0.600 M sodium acetate. Use 1.80 × 10−5 as Ka for acetic acid.(c) What is the pH of a solution that results when 3.00 mL of 0.034 M HCl is added to 0.200 L of the original buffer?
The normal pH of blood is 7.40 ± 0.05 and is controlled in part by the H  2CO3/HCO3− buffer system.(a) Assuming that the Ka value for carbonic acid at 25°C applies to blood, what is the [H2CO3]/[HCO3−] ratio in normal blood?
A 5.36–g sample of NH4Cl was added to 25.0 mL of 1.00 M NaOH and the resulting solution diluted to 0.100 L.(a) What is the pH of this buffer solution?
A 5.36–g sample of NH4Cl was added to 25.0 mL of 1.00 M NaOH and the resulting solution diluted to 0.100 L.(b) Is the solution acidic or basic?
A 5.36–g sample of NH4Cl was added to 25.0 mL of 1.00 M NaOH and the resulting solution diluted to 0.100 L.(c) What is the pH of a solution that results when 3.00 mL of 0.034 M HCl is added to the solution?
The normal pH of blood is 7.40 ± 0.05 and is controlled in part by the H  2CO3/HCO3− buffer system.(b) In a condition called acidosis, the blood is too acidic. What is the [H 2CO3]/[HCO3−] ratio in a patient whose blood pH is 7.20?
A bioengineer preparing cells for cloning bathes a small piece of rat epithelial tissue in a TRIS buffer (see Problem 19.109). The buffer is made by dissolving 43.0 g of TRIS (pKb = 5.91) in enough 0.095 M HCl to make 1.00 L of solution. What are the molarity of TRIS and the pH of the buffer?Problem 19.109. Tris(hydroxymethyl)aminomethane [(HOCH2)3CNH2], known as TRIS, is a weak base used in biochemical experiments to make buffer solutions in the pH range of 7 to 9. A certain TRIS buffer has a pH of 8.10 at 25°C and a pH of 7.80 at 37°C. Why does the pH change with temperature?
What is the component concentration ratio, [Pr−]/[HPr], of a buffer that has a pH of 5.44 (Ka of HPr = 1.3×10−5)?
What is the component concentration ratio, [NO2 −]/[HNO2], of a buffer that has a pH of 2.95 (Ka of HNO2 = 7.1×10−4)?
What is the component concentration ratio, [BrO−]/[HBrO], of a buffer that has a pH of 7.95 (Ka of HBrO = 2.3 × 10−9)?
Calculate the pH of a solution that is 0.27 M in HF and 0.11 M in NaF. Express your answer using two decimal places.
What is the component concentration ratio, [CH3COO−]/ [CH3COOH], of a buffer that has a pH of 4.39 (Ka of CH3COOH = 1.8 × 10−5)?
Amino acids [general formula NH 2CH(R)COOH] can be considered polyprotic acids. In many cases, the R group contains additional amine and carboxyl groups.(a) Can an amino acid dissolved in pure water have a protonated COOH group and an unprotonated NH2 group (Ka of COOH group = 4.47 × 10−3; Kb of NH2 group = 6.03 × 10−5)? Use glycine, NH2CH2COOH, to explain why.
A buffer containing 0.2000 M of acid, HA, and 0.1500 M of its conjugate base, A −, has a pH of 3.35. What is the pH after 0.0015 mol of NaOH is added to 0.5000 L of this solution?
A buffer that contains 0.40 M of a base, B, and 0.25 M of its conjugate acid, BH  +, has a pH of 8.88. What is the pH after 0.0020 mol of HCl is added to 0.25 L of this solution?
Amino acids [general formula NH 2CH(R)COOH] can be considered polyprotic acids. In many cases, the R group contains additional amine and carboxyl groups.(b) Calculate [+NH3CH2COO−]/[+NH3CH2COOH] at pH 5.5. 
A buffer that contains 0.110 M HY and 0.220 M Y − has a pH of 8.77. What is the pH after 0.0015 mol of Ba(OH)2 is added to 0.350 L of this solution?
Calculate the pH of a buffer solution that is 0.60 M in NH4Cl and 0.75 M in NH3. (K b = 1.8 × 10−5 for NH3) a. 9.16 b. 11.60 c. 9.35 d. 4.84  
A buffer that contains 1.05 M B and 0.750 M BH + has a pH of 9.50. What is the pH after 0.0050 mol of HCl is added to 0.500 L of this solution?
a. Calculate the pH of 0.250 L of a 0.36 M formic acid-0.30 M sodium formate buffer. Express your answer using three significant figures.   b. After the addition of 0.0050 mol of NaOH. Assume that the volume remains constant. Express your answer using three significant figures.   c. After the addition of 0.0050 mol of HCl. Assume that the volume remains constant. Express your answer using three significant figures.
A buffer is prepared by mixing 204 mL of 0.452 M HCl and 0.500 L of 0.400 M sodium acetate. (See Appendix C.) (a) What is the pH?
Consider 1.0 L of a solution that is 0.85 M HOC 6H5 and 0.80 M NaOC6H5. (Ka for HOC6H5 = 1.6 x 10 -10.)a. Calculate the pH of this solution.
A buffer is prepared by mixing 204 mL of 0.452 M HCl and 0.500 L of 0.400 M sodium acetate. (See Appendix C.) (b) How many grams of KOH must be added to 0.500 L of the buffer to change the pH by 0.15 units?
A buffer is prepared by mixing 50.0 mL of 0.050 M sodium bicarbonate and 10.7 mL of 0.10 M NaOH. (See Appendix C.)(a) What is the pH?
Consider 1.0 L of a solution that is 0.85 M HOC 6H5 and 0.80 M NaOC6H5. (Ka for HOC6H5 = 1.6 x 10 -10.)b. Calculate the pH after 0.10 mole of HCl has been added to the original solution. Assume no volume change on addition of HCl.
A buffer is prepared by mixing 50.0 mL of 0.050 M sodium bicarbonate and 10.7 mL of 0.10 M NaOH. (See Appendix C.)(b) How many grams of HCl must be added to 25.0 mL of the buffer to change the pH by 0.07 units?
Consider 1.0 L of a solution that is 0.85 M HOC 6H5 and 0.80 M NaOC6H5. (Ka for HOC6H5 = 1.6 x 10 -10.)c. Calculate the pH after 0.20 mole of NaOH has been added to the original buffer solution. Assume no volume change on addition of NaOH.
What concentration of NH4Cl is necessary to buffer a 0.52-M NH 3 solution at pH = 9.00? (Kb for NH3 = 1.8 x 10 -5.)
Muscle physiologists study the accumulation of lactic acid [CH 3CH(OH)COOH] during exercise. Food chemists study its occurrence in sour milk, beer, wine, and fruit. Industrial microbiologists study its formation by various bacterial species from carbohydrates. A biochemist prepares a lactic acid–lactate buffer by mixing 225 mL of 0.85 M lactic acid (Ka = 1.38 × 10−4) with 435 mL of 0.68 M sodium lactate. What is the buffer pH?
A 500.-mL solution consists of 0.050 mol of solid NaOH and 0.13 mol of hypochlorous acid (HClO; Ka = 3.0 × 10−8) dissolved in water.(a) Aside from water, what is the concentration of each species that is present?
Many moderately large organic molecules containing basic nitrogen atoms are not very soluble in water as neutral molecules, but they are frequently much more soluble as their acid salts. Assuming that pH in the stomach is 2.5, indicate whether each of the following compounds would be present in the stomach as the neutral base or in the protonated form:nicotine, Kb = 7x10-7
Derive an equation analogous to the Henderson–Hasselbalch equation but relating pOH and pKb of a buffered solution composed of a weak base and its conjugate acid, such as NH 3 and NH4+.
A 500.-mL solution consists of 0.050 mol of solid NaOH and 0.13 mol of hypochlorous acid (HClO; Ka = 3.0 × 10−8) dissolved in water.(b) What is the pH of the solution?
Many moderately large organic molecules containing basic nitrogen atoms are not very soluble in water as neutral molecules, but they are frequently much more soluble as their acid salts. Assuming that pH in the stomach is 2.5, indicate whether each of the following compounds would be present in the stomach as the neutral base or in the protonated form:caffeine, Kb = 4x10-14
a. Calculate the pH of a buffered solution that is 0.100 M in C 6H5CO2H (benzoic acid, Ka = 6.4 x 10-5) and 0.100 M in C6H5CO2Na.
A 500.-mL solution consists of 0.050 mol of solid NaOH and 0.13 mol of hypochlorous acid (HClO; Ka = 3.0 × 10−8) dissolved in water.(c) What is the pH after adding 0.0050 mol of HCl to the flask?
Many moderately large organic molecules containing basic nitrogen atoms are not very soluble in water as neutral molecules, but they are frequently much more soluble as their acid salts. Assuming that pH in the stomach is 2.5, indicate whether each of the following compounds would be present in the stomach as the neutral base or in the protonated form:strychnine, Kb = 1x10-6
Calculate the pH of a buffered solution that is 0.100 M in C6H5CO2H (benzoic acid, Ka = 6.4 x 10-5) and 0.100 M in C6H5CO2Na.b. Calculate the pH after 20.0% (by moles) of the benzoic acid is converted to benzoate anion by addition of a strong base. Use the dissociation equilibrium C6H5CO2H (aq) ⇌ C6H5CO2- (aq) + H+ (aq)to calculate the pH.
Many moderately large organic molecules containing basic nitrogen atoms are not very soluble in water as neutral molecules, but they are frequently much more soluble as their acid salts. Assuming that pH in the stomach is 2.5, indicate whether each of the following compounds would be present in the stomach as the neutral base or in the protonated form:quinine, Kb = 1.1x10-6
Calculate the pH of each of the following solutions.a. 0.100 M propanoic acid (HC3H5O2, Ka = 1.3 x 10-5)
Calculate the pH of a buffered solution that is 0.100 M in C6H5CO2H (benzoic acid, Ka = 6.4 x 10-5) and 0.100 M in C6H5CO2Na.c. Calculate the pH after 20.0% (by moles) of the benzoic acid is converted to benzoate anion by addition of a strong base. Use the following equilibrium to calculate the pH:C6H5CO2- (aq) + H2O (l) ⇌ C6H5CO2H (aq) + OH - (aq)
An industrial chemist studying bleaching and sterilizing prepares several hypochlorite buffers. Find the pH of(a) 0.100 M HClO and 0.100 M NaClO;
a. Calculate the pH of a buffered solution that is 0.100 M in C6H5CO2H (benzoic acid, Ka = 6.4 x 10-5) and 0.100 M in C6H5CO2Na.b. Calculate the pH after 20.0% (by moles) of the benzoic acid is converted to benzoate anion by addition of a strong base. Use the dissociation equilibrium C6H5CO2H (aq) ⇌ C6H5CO2- (aq) + H+ (aq)to calculate the pH.c. Calculate the pH after 20.0% (by moles) of the benzoic acid is converted to benzoate anion by addition of a strong base. Use the following equilibrium to calculate the pH:C6H5CO2- (aq) + H2O (l) ⇌ C6H5CO2H (aq) + OH - (aq)d. Do your answers in parts b and c agree? Explain.
An industrial chemist studying bleaching and sterilizing prepares several hypochlorite buffers. Find the pH of(b) 0.100 M HClO and 0.150 M NaClO;
Calculate the pH of each of the following solutions.a. 0.100 M HONH2 (Kb = 1.1 x 10 -8)
An industrial chemist studying bleaching and sterilizing prepares several hypochlorite buffers. Find the pH of(c) 0.150 M HClO and 0.100 M NaClO;
Tris(hydroxymethyl)aminomethane, commonly called TRIS or Trizma, is often used as a buffer in biochemical studies. Its buffering range is pH 7 to 9, and Kb is 1.19 x 10-6 for the aqueous reactionb. Calculate the ratio [TRIS] / [TRISH+] at pH = 7.00 and at pH = 9.00.
Human blood contains one buffer system based on phosphate species and one based on carbonate species. Assuming that blood has a normal pH of 7.4, what are the principal phosphate and carbonate species present? What is the ratio of the two phosphate species? (In the presence of the dissolved ions and other species in blood, Ka1 of H3PO4 = 1.3 × 10−2, Ka2 = 2.3 × 10−7, and Ka3 = 6 × 10−12; Ka1 of H2CO3 = 8 × 10−7 and Ka2 = 1.6 × 10−10.)
Compare the percent dissociation of 0.100 M propanoic acid (HC3H5O2, Ka = 1.3 x 10-5) with the percent dissociation of the acid mixture containing 0.100 M HC3H5O2 and 0.100 M NaC3H5O2. Explain the large difference in percent dissociation of the acid.
Tris(hydroxymethyl)aminomethane, commonly called TRIS or Trizma, is often used as a buffer in biochemical studies. Its buffering range is pH 7 to 9, and Kb is 1.19 x 10-6 for the aqueous reactionc. A buffer is prepared by diluting 50.0 g TRIS base and 65.0 g TRIS hydrochloride (written as TRISHCl) to a total volume of 2.0 L. What is the pH of this buffer? What is the pH after 0.50 mL of 12 M HCl is added to a 200.0-mL portion of the buffer?
Oxoanions of phosphorus are buffer components in blood. For a KH 2PO4/Na2HPO4 buffer with pH = 7.40 (pH of normal arterial blood), what is the buffer-component concentration ratio?
Compare the percent ionization of the base 0.100 M HONH2 (Kb = 1.1 x 10-8) with the percent ionization of the base mixture containing 0.100 M HONH2 and 0.100 M HONH3Cl. Explain any differences.
You make 1.00 L of a buffered solution (pH = 4.00) by mixing acetic acid and sodium acetate. You have 1.00 M solutions of each component of the buffered solution. What volume of each solution do you mix to make such a buffered solution?
Calculate the pH after 0.020 mole of HCl is added to 1.00 L of each of the following solutions:a. 0.100 M propanoic acid (HC3H5O2, Ka = 1.3 x 10-5)b. 0.100 M sodium propanoate (NaC3H5O2)c. pure H2Od. a mixture containing 0.100 M HC3H5O2 and 0.100 M NaC3H5O2
You have the following reagents on hand:What combinations of reagents would you use to prepare buffers at the following pH values?a. 3.0 
Calculate the pH after 0.020 mole of HCl is added to 1.00 L of each of the following solutions:a. 0.100 M HONH2 (Kb = 1.1 x 10-8)b. 0.100 M HONH3Clc. pure H2Od. a mixture containing 0.100 M HONH2 and 0.100 M HONH3Cl
You have the following reagents on hand:What combinations of reagents would you use to prepare buffers at the following pH values?b. 4.0
You have the following reagents on hand:What combinations of reagents would you use to prepare buffers at the following pH values?c. 5.0
You have the following reagents on hand:What combinations of reagents would you use to prepare buffers at the following pH values?d. 7.0
You are asked to prepare a pH = 4 buffer starting from 1.50L of .02 M solution of benzoic acid and an excess of sodium benzoate. a. What is the pH of the benzoic acid solution prior to adding sodium benzoate? b. How many grams of sodium benzoate should be added to prepare the buffer? Neglect the small volume change that occurs when the sodium benzoate is added.
Calculate the pH after 0.020 mole of NaOH is added to 1.00 L of each of the following solutions:a. 0.100 M propanoic acid (HC3H5O2, Ka = 1.3 x 10-5)b. 0.100 M sodium propanoate (NaC3H5O2)c. pure H2Od. a mixture containing 0.100 M HC3H5O2 and 0.100 M NaC3H5O2
You have the following reagents on hand:What combinations of reagents would you use to prepare buffers at the following pH values?e. 9.0
Calculate the pH after 0.020 mole of NaOH is added to 1.00 L of each of the following solutions:a. 0.100 M HONH2 (Kb = 1.1 x 10-8)b. 0.100 M HONH3Clc. pure H2Od. a mixture containing 0.100 M HONH2 and 0.100 M HONH3Cl
Saccharin, C7H4NSO3H, is a weak acid (Ka = 2.1 × 10−2). If 0.250 L of diet cola with a buffered pH of 5.48 was prepared from 2.00 × 10−3 g of sodium saccharide, Na(C7H4NSO3), what are the final concentrations of saccharine and sodium saccharide in the solution?
Phosphate buffers are important in regulating the pH of intracellular fluids at pH values generally between 7.1 and 7.2. a. What is the concentration ratio of H 2PO4- to HPO42- in intracellular fluid at pH = 7.15?H2PO4- (aq) ⇌ HPO42- (aq) + H+ (aq)            K a = 6.2 x 10-8
A biochemist needs a medium for acid-producing bacteria. The pH of the medium must not change by more than 0.05 pH units for every 0.0010 mol of H3O+ generated by the organisms per liter of medium. A buffer consisting of 0.10 M HA and 0.10 M A− is included in the medium to control its pH. What volume of this buffer must be included in 1.0 L of medium?
Which of the following solutions is a buffered solution?a. 0.100 M HONH2 (Kb = 1.1 x 10-8)b. 0.100 M HONH3Clc. pure H2Od. a mixture containing 0.100 M HONH2 and 0.100 M HONH3Cl
Which solution is a buffer?(a) a solution that is 0.100 M in HNO2 and 0.100 M in HCl(b) a solution that is 0.100 M in HNO3 and 0.100 M in NaNO3(c) a solution that is 0.100 M in HNO2 and 0.100 M in NaCl(d) a solution that is 0.100 M in HNO2 and 0.100 M in NaNO2
A buffer is 0.100 M in NH4Cl and 0.100 M in NH3. When a small amount of hydrobromic acid is added to this buffer, which buffer component neutralizes the added acid?
Consider a buffer composed of the weak acid HA and its conjugate base A–. Which pair of concentrations results in the most effective buffer?a) 0.10 M HA; 0.10 M A–b) 0.50 M HA; 0.50 M A–c) 0.90 M HA; 0.10 M A–d) 0.10 M HA; 0.90 M A–
Scenes A to D represent tiny portions of 0.10 M aqueous solutions of a weak acid HA (red and blue; Ka = 4.5×10−5), its conjugate base A−(red), or a mixture of the two (only these two species are shown):(a) Which scene(s) show(s) a buffer?
You may want to refernce(Pages 792 - 794)Section 17.3 while completing this problem.Which acid is the best choice to create a buffer with pH = 7.38?a. Chlorous acid (HClO2) pKa = 1.95b. Formic acid (HCHO2) pKa = 3.74c. Nitrous acid (HNO2) pKa = 3.34d. Hypochlorous acid (HClO) pKa = 7.54
Which of the following mixtures would result in buffered solutions when 1.0 L of each of the two solutions are mixed? a. 0.1 M KOH and 0.1 M CH 3NH3Clb. 0.1 M KOH and 0.2 M CH 3NH2c. 0.2 M KOH and 0.1 M CH 3NH3Cld. 0.1 M KOH and 0.2 M CH 3NH3Cl
Which of the following mixtures would result in a buffered solution when 1.0 L of each of the two solutions are mixed? a. 0.2 M HNO3 and 0.4 M NaNO3b. 0.2 M HNO3 and 0.4 M HFc. 0.2 M HNO3 and 0.4 M NaFd. 0.2 M HNO3 and 0.4 M NaOH
Name a compound that you could add to a solution of each of the compounds to make a buffer. Explain your reasoning in complete sentences.a. acetic acidb. sodium nitritec. ammoniad. potassium formatee. Na2HPO4 (two possible answers)
The fluids within cells are buffered by H2PO4– and HPO42–. Could a buffer system employing H3PO4 as the weak acid and H2PO4– as the weak base be used as a buffer system within cells?
Explain why a buffer can be prepared from a mixture of NH 4Cl and NaOH but not from NH3 and NaOH.
An equal volume mixture of which two solutions will produce a buffer solution? a. 1 M HClO4 and 1 M KClO4 b. 2 M HC2H3O2 and 1 M KOH c. 1 M NH3 and 1 M HCl d. 1 M HF and 2 M NaOH  
How many of the following are buffered solutions? Explain your answer. Note: Counter-ions and water molecules have been omitted from the illustrations for clarity.
Which of the following can be classified as buffer solutions?a. 0.25 M HBr + 0.25 M HOBrb. 0.15 M HClO4 + 0.20 M RbOHc. 0.50 M HOCl + 0.35 M KOCld. 0.70 M KOH + 0.70 M HONH 2e. 0.85 M H2NNH2 + 0.60 M H2NNH3NO3
Which of the following are valid ways to make an ammonia/ammonium buffer for use in a laboratory? Explain your choices. A) mix equal volumes of 1 M NH3 and 1 M NH4+  B) Mix equal volumes of 1 M NH3 and 0.01 M NH4+  C) Mix equal volumes of 1 M NH3 and 1 M HCl D) Mix some volume of 1 M NH3 and half as much HCl
Calculate the pH of a solution that is 0.230 M in benzoic acid and 0.130 M in sodium benzoate, a salt whose anion is the conjugate base of benzoic acid.
Calculate the pH of a solution that is 0.170 M in benzoic acid and 0.190 M in sodium benzoate, a salt whose anion is the conjugate base of benzoic acid.
What is the ratio of acetate ion to acetic acid (Ka = 1.76 times 10-5) in a buffer containing these compounds at pH 4.560?
Calculate the ratio of CH3NH2 to CH3NH3Cl required to create a buffer with pH = 10.28. Express your answer using two significant figures. 
What is the pH change of a 0.210 M solution of citric acid (pKa = 4.77) if citrate is added to a concentration of 0.125 M with no change in volume? Express the difference in pH numerically to two decimal places.
If a buffer solution is 0.140 M in a weak acid (K_a = 8.1 times 10^-5) and 0.450 M in its conjugate base, what is the pH?
What is the pH of 1.00 L of a buffer that is 120 M nitrous acid (HNO2) and 0.170 M NaNO2? pKa of HNO2 = 3.40
The Ka of nitrous acid, HNO2, is 4.5x10-4. What [NO2-]/[HNO2] ratio is necessary to make a buffer with a pH of 3.71?a) 1.9 x 10-8b) 0.45c) 0.76d) 1.5e) 2.3
Determine the pH change when 0.091 mol KOH is added to 1.00 L of a buffer solution that is 0.324 M in HNO2 and 0.297 M in NO2-. pH after addition - pH before addition = pH change =
A buffer solution made from HCIO and NaCIO has a pH of 7.20.If pKa for HCIO is 7.46, what is the [CIO-]/[HCIO] in the buffer? 
What is the ratio of acetate ion to acetic acid (K a = 1.76 x 10 -5) in a buffer containing these compounds at pH 4.570? 
Write the Henderson-Hasselbalch equation for a propanoic acid solution (CH3CH2CO2H, pKa = 4.874) using the symbols HA and A -, and the given pKa value for propanoic acid in the expression. pH = pKa + log [A-] / [HA]Using the equation above, calculate the quotient [A-] / [HA] at a) pH 4.112. b) pH 4.874. c) pH 5.115.
If a buffer solution is 0.220 M in a weak base (K b 8.6 x 10-5) and 0.590 M in its conjugate acid, what is the pH? 
You need to prepare 100.0 mL of a pH=4.00 buffer solution using 0.100 M benzoic acid (pKa = 4.20) and 0.160 M sodium benzoate. How much of each solution should be mixed to prepare this buffer?
A buffer solution is prepared by adding 0.121 mol of ammonium chloride to 5.00 times 10^2 mL of 0.544 M solution of ammonia. What is the pH of the buffer? Ka = 5.6 times 10^-10 A buffer solution is prepared by adding 0.121 mol of ammonium chloride to 5.00 times 10^2 mL of 0.544 M solution of ammonia. If 0.0110 mol of NCI gas is bubbled into 5.00 times 10^2 mL of the buffer, what is the new pH of the solution? Ka = 5.6 times 10^-10
a) The Ka for acetic acid (H3CCO2H) is 1.737 x 10-5. What is the pKa for this acid? b) use the pKa calculated above to determine the pH at which [H3CCO2H] = [H3CCO2-]
Calculate the pH of a solution that is 0.220 mol L-1 in nitrous acid (HNO2) and 0.300 mol L-1 in potassium nitrite (KNO2). The acid dissociation constant of nitrous acid is 4.50x10-4. 12.820, 3.481, 4.527, 10.519, 3.212
A buffer solution is made using a weak acid, HA, that has a pK a of 6. If the pH of the buffer is 8, what is the ratio of A- to HA?
Which one of the following pairs  cannot be mixed together to form a buffer solution?
What is the final pH when 42.1 mL of 3.2 M NaOH is added to 1.00 L of 0.150 M HF (Ka = 3.5 x 10 -4)
What mass of ammonium chloride (NH 4Cl, molar mass 53.5g/mol) must be added to a 0.500mL solution of 0.250M ammonia to make a buffer with a pH of 9.26?
A buffer solution is 0.280 M in a weak base (K b = 3.5 x 10 -5) and 0.550 M in its conjugate acid, what is the pH?
Nitric acid, HNO2 is a weak acid with Ka= 4.5 x 10-4. It dissociates according to:HNO2 (aq) ⇌ H+(aq) + NO2-(aq)a.) What is the pH of a buffer solution which is 0.80 M in NO2- and 0.40 M in HNO2?  b.) What will be the pH of the resulting solution when 2.0 mL of 0.5 M HCl are added to 50 mL of this (from part a) buffer solution?   c.) What will be the pH of the resulting solution when 2.0 mL of 0.5 M NaOH are added to 50 mL of this (from part a) buffer solution?
Which of the following solutions is a buffer?a. A solution made by mixing 100 mL of 0.100 M KClO and 50 mL of 0.100 M KCl.b. A solution made by mixing 100 mL of 0.100 M HClO and 500 mL of 0.100 M NaOH.c. A solution made by mixing 100 mL of 0.100 M HClO and 50 mL of 0.100 M NaOH.d. A solution made by mixing 100 mL of 0.100 M HClO and 50 mL of 0.100 M HCl.
A 100.0 mL buffer solution is 0.175 M in HClO and 0.150 M in NaClO. What is the pH after addition of 0.090 g of NaOH?
500.0 mL of 0.110 M NaOH is added to 575 mL of 0.200 M weak acid (K   a = 7.16 x 10-6). What is the pH of the resulting buffer? HA (aq) + OH - (aq) → H2O (l) + A- (aq) 
You need to prepare 100.0 mL of a pH=4.00 buffer solution using 0.100 M benzoic acid (pKa = 4.20) and 0.140 M sodium benzoate. How much of each solution should be mixed to prepare this buffer?
The Ka of acetic acid is 1.8 x 10-5 at 25°C.a) What is the pH of a 0.5 M solution of acetic acid at 25°C?b)What is the pH of a solution made up of 20 mL of 0.5 M solution of acetic acid and 10 mL of 0.5 M sodium acetate?c) If 10 mL of 0.1 M NaOH is added to the solution in part b, what is the final pH?d) What is the pH of a solution containing equal concentrations of acetic acid and sodium acetate?
A buffer solution is made using a weak acid. HA, that has a pKa of 5. If the pH of the buffler is 6, what is the ratio of A- to HA? 
Which pair of compounds act as a buffer in aqueous solution?a. H3PO4 (phosphoric acid) and H2PO4- (dihydrogen phosphate ion)b. NaCN (sodium cyanide) and KOH (potassium hydroxide)c. HCIO4 (perchloric acid) and NaOH (sodium hydroxide) 
You need to prepare 100.0 mL of a pH = 4.00 buffer solution using 0.100 M benzoic acid (pKa = 4.20) and 0.180 M sodium benzoate. How much of each solution should be mixed to prepare this buffer?
How could you make a buffer? Select all that apply.a) Partially neutralize a weak base solution by addition of a strong acid.b) Add appropriate quantities of weak acid and its conjugate base to water.c) Partially neutralize a strong acid solution by addition of a strong base.d) Partially neutralize a weak acid solution by addition of a strong base.e) Partially neutralize a strong base solution by addition of a strong acid.
Which of the following statements are TRUE of buffer solutions?1. A buffer solution can be made by mixing equal concentrations of acetic acid and sodium acetate.2. A buffer solution can be made by mixing equal concentrations of hydrochloric acid and sodium chloride.3. A buffer solution resists changes in pH when small quantities of acid or base are added.a. 1 and 3 onlyb. 1 and 2 onlyc. 2 and 3 onlyd. All of 1, 2, and 3e. None of 1, 2, and 3
Which set of compounds would form a buffer in aqueous solution?HBr and NaBrHCl and HClONaF and KFHF and KFNaF and NaOHNaCl and KClHCN and NaCN
a) Calculate the percent ionization of a 0.16M benzoic acid solution in pure water.b) Calculate the percent ionization of a 0.16M benzoic acid solution in a solution containing 0.11M sodium benzoate.
Which set of compounds would form a buffer in aqueous solution? HCOOH and HCOONa HF and NaF NaCl and KCl HF and KCN HBr and NaBr NaBr and KBr NaCl and NaOH
A buffer solution contains 0.323 M KHSO3, and 0.257 M K2SO3.If 0.0495 moles of sodium hydroxide are added to 250. mL of this buffer, what is the pH of the resulting solution?(Assume that the volume does not change upon adding sodium hydroxide)pH =
What is the pH of a solution containing 0.015 M CH3CH(OH)COOH and 0.018 M CH3CH(OH)COO (made by dissolving CH_3 CH(OH)COONa)? The Ka for CH3CH(OH)COOH is 0.000839
Use the Henderson-Hasselbalch equation to calculate the pH of each solution: A solution that is 0.15 Min HCHO2 and 0.15 Min NaCHO2 Express your answer using two decimal places.
Benzoic acid (C7H6O2) is a weak acid whose Ka is 6.5 x 10-5. If 0.490 g of benzoic acid are dissolved in 250 ml of water what mass of sodium benzoate (NaC7H5O2) would need to be added to adjust the pH of of the solution to 5.20? (You may assume that the added sodium benzoate doesn't significantly change the solution volume).
Which pair of compounds will form a buffer in aqueous solution?a. NaCN and NaOHb. NaCN and KCNc. HCl and NaOHd. HCN and NaCNe. HCN and HClf. HCl and NaCl
Of the following solutions, which has the greatest buffering capacity?a. 0.296 M HF and 0.122 M NaFb. 0.195 M HF and 8.02 x 10−2 M NaFc. 0.591 M HF and 0.243 M NaFd. 1.18 M HF and 0.486 M NaFe. They are all buffer solutions and would all have the same capacity.